<h1 dir="auto">Checklist</h1>

<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have verified that the issue exists against the <code class="notranslate">master</code> branch of Celery.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> This has already been asked to the <a href="https://groups.google.com/forum/#!forum/celery-users" rel="nofollow">discussion group</a> first.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have read the relevant section in the<br>
<a href="http://docs.celeryproject.org/en/latest/contributing.html#other-bugs" rel="nofollow">contribution guide</a><br>
on reporting bugs.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have checked the <a href="https://github.com/celery/celery/issues?q=is%3Aissue+label%3A%22Issue+Type%3A+Bug+Report%22+-label%3A%22Category%3A+Documentation%22">issues list</a><br>
for similar or identical bug reports.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have checked the <a href="https://github.com/celery/celery/pulls?q=is%3Apr+label%3A%22PR+Type%3A+Bugfix%22+-label%3A%22Category%3A+Documentation%22">pull requests list</a><br>
for existing proposed fixes.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have checked the <a href="https://github.com/celery/celery/commits/master">commit log</a><br>
to find out if the bug was already fixed in the master branch.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have included all related issues and possible duplicate issues<br>
in this issue (If there are none, check this box anyway).</li>
</ul>
<h2 dir="auto">Mandatory Debugging Information</h2>
<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have included the output of <code class="notranslate">celery -A proj report</code> in the issue.<br>
(if you are not able to do this, then at least specify the Celery<br>
version affected).</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have verified that the issue exists against the <code class="notranslate">master</code> branch of Celery.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have included the contents of <code class="notranslate">pip freeze</code> in the issue.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have included all the versions of all the external dependencies required<br>
to reproduce this bug.</li>
</ul>
<h2 dir="auto">Optional Debugging Information</h2>

<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue on more than one Python version<br>
and/or implementation.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue on more than one message broker and/or<br>
result backend.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue on more than one version of the message<br>
broker and/or result backend.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have tried reproducing the issue on more than one operating system.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have tried reproducing the issue on more than one workers pool.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue with autoscaling, retries,<br>
ETA/Countdown &amp; rate limits disabled.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue after downgrading<br>
and/or upgrading Celery and its dependencies.</li>
</ul>
<h2 dir="auto">Related Issues and Possible Duplicates</h2>

<h4 dir="auto">Related Issues</h4>
<ul dir="auto">
<li>None</li>
</ul>
<h4 dir="auto">Possible Duplicates</h4>
<ul dir="auto">
<li>None</li>
</ul>
<h2 dir="auto">Environment &amp; Settings</h2>

<p dir="auto"><strong>Celery version</strong>:<br>
4.4.0 (cliffs)</p>

<details>
<summary><b><code class="notranslate">celery report</code> Output:</b></summary>
<p dir="auto">
```
software -&gt; celery:4.4.0 (cliffs) kombu:4.6.7 py:3.7.3
            billiard:3.6.2.0 py-amqp:2.5.2
platform -&gt; system:Linux arch:64bit, ELF
            kernel version:4.4.0-43-Microsoft imp:CPython
loader   -&gt; celery.loaders.app.AppLoader
settings -&gt; transport:amqps results:disabled
</p><p dir="auto">broker_url: 'amqps://xxxxxxxxxxxxxxxxxx:********@xxx.xxx.xxx.xxx:5671/xxxxxxxxxxxxxx'<br>
result_extended: True<br>
worker_send_task_events: True</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="
&lt;/p&gt;
&lt;/details&gt;

# Steps to Reproduce

## Required Dependencies
&lt;!-- Please fill the required dependencies to reproduce this issue --&gt;
* **Minimal Python Version**: 3.7.3
* **Minimal Celery Version**: 4.4.0
* **Minimal Kombu Version**: 4.6.7
* **Minimal Broker Version**: N/A or Unknown
* **Minimal Result Backend Version**: N/A or Unknown
* **Minimal OS and/or Kernel Version**: Linux xxxx 4.4.0-43-Microsoft #1-Microsoft Wed Dec 31 14:42:53 PST 2014 x86_64 GNU/Linux
* **Minimal Broker Client Version**: N/A or Unknown
* **Minimal Result Backend Client Version**: N/A or Unknown

### Python Packages
&lt;!-- Please fill the contents of pip freeze below --&gt;
&lt;details&gt;
&lt;summary&gt;&lt;b&gt;&lt;code&gt;pip freeze&lt;/code&gt; Output:&lt;/b&gt;&lt;/summary&gt;
&lt;p&gt;
"><pre class="notranslate"><code class="notranslate">
&lt;/p&gt;
&lt;/details&gt;

# Steps to Reproduce

## Required Dependencies
&lt;!-- Please fill the required dependencies to reproduce this issue --&gt;
* **Minimal Python Version**: 3.7.3
* **Minimal Celery Version**: 4.4.0
* **Minimal Kombu Version**: 4.6.7
* **Minimal Broker Version**: N/A or Unknown
* **Minimal Result Backend Version**: N/A or Unknown
* **Minimal OS and/or Kernel Version**: Linux xxxx 4.4.0-43-Microsoft #1-Microsoft Wed Dec 31 14:42:53 PST 2014 x86_64 GNU/Linux
* **Minimal Broker Client Version**: N/A or Unknown
* **Minimal Result Backend Client Version**: N/A or Unknown

### Python Packages
&lt;!-- Please fill the contents of pip freeze below --&gt;
&lt;details&gt;
&lt;summary&gt;&lt;b&gt;&lt;code&gt;pip freeze&lt;/code&gt; Output:&lt;/b&gt;&lt;/summary&gt;
&lt;p&gt;

</code></pre></div>
<p dir="auto">amqp==2.5.2<br>
aniso8601==8.0.0<br>
astroid==2.3.3<br>
attrs==19.3.0<br>
billiard==3.6.2.0<br>
celery==4.4.0<br>
Click==7.0<br>
cx-Oracle==7.3.0<br>
Flask==1.1.1<br>
flask-restplus==0.13.0<br>
flask-restx==0.1.0<br>
Flask-SQLAlchemy==2.4.1<br>
importlib-metadata==1.5.0<br>
isort==4.3.21<br>
itsdangerous==1.1.0<br>
Jinja2==2.11.1<br>
jsonschema==3.2.0<br>
kombu==4.6.7<br>
lazy-object-proxy==1.4.3<br>
MarkupSafe==1.1.1<br>
mccabe==0.6.1<br>
pkg-resources==0.0.0<br>
pylint==2.4.4<br>
pyrsistent==0.15.7<br>
pytz==2019.3<br>
PyYAML==5.3<br>
six==1.14.0<br>
SQLAlchemy==1.3.13<br>
typed-ast==1.4.1<br>
vine==1.3.0<br>
waitress==1.4.3<br>
Werkzeug==0.16.1<br>
wrapt==1.11.2<br>
zipp==2.1.0</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="
&lt;/p&gt;
&lt;/details&gt;

### Other Dependencies
&lt;!--
Please provide system dependencies, configuration files
and other dependency information if applicable
--&gt;
&lt;details&gt;
&lt;p&gt;
Distro is Debian GNU/Linux 10 \n \l
&lt;/p&gt;
&lt;/details&gt;

## Minimally Reproducible Test Case
&lt;!--
Please provide a reproducible test case.
Refer to the Reporting Bugs section in our contribution guide.

We prefer submitting test cases in the form of a PR to our integration test suite.
If you can provide one, please mention the PR number below.
If not, please attach the most minimal code example required to reproduce the issue below.
If the test case is too large, please include a link to a gist or a repository below.
--&gt;

&lt;details&gt;
&lt;p&gt;
"><pre class="notranslate"><code class="notranslate">
&lt;/p&gt;
&lt;/details&gt;

### Other Dependencies
&lt;!--
Please provide system dependencies, configuration files
and other dependency information if applicable
--&gt;
&lt;details&gt;
&lt;p&gt;
Distro is Debian GNU/Linux 10 \n \l
&lt;/p&gt;
&lt;/details&gt;

## Minimally Reproducible Test Case
&lt;!--
Please provide a reproducible test case.
Refer to the Reporting Bugs section in our contribution guide.

We prefer submitting test cases in the form of a PR to our integration test suite.
If you can provide one, please mention the PR number below.
If not, please attach the most minimal code example required to reproduce the issue below.
If the test case is too large, please include a link to a gist or a repository below.
--&gt;

&lt;details&gt;
&lt;p&gt;

</code></pre></div>
<p dir="auto">from celery import Celery, group<br>
from time import sleep</p>
<p dir="auto">mqconfig = ['rabbitmqhost1', 'rabbitmqhost2', 'rabbitmqhost3']</p>
<p dir="auto">app = Celery('acdid', broker=mqconfig)</p>
<p dir="auto">app.conf.result_extended = True<br>
app.conf.worker_send_task_events = True</p>
<p dir="auto">@app.task()<br>
def addacd(id):<br>
sleep(2)<br>
results = 'Sucessfully added: {}'.format(id)<br>
print(results)<br>
return results</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="
&lt;/p&gt;
&lt;/details&gt;

# Expected Behavior
&lt;!-- Describe in detail what you expect to happen --&gt;
After starting my worker instance using celery worker -A acdworker -l info, I should be able to perform a warm shutdown by doing ctrl-c.

'''
celery worker -A acdworker -l info
&lt;startup text&gt;
^C
worker: Hitting Ctrl+C again will terminate all running tasks!
worker: Warm shutdown (MainProcess)
'''
# Actual Behavior
&lt;!--
Describe in detail what actually happened.
Please include a backtrace and surround it with triple backticks (```).
In addition, include the Celery daemon logs, the broker logs,
the result backend logs and system logs below if they will help us debug
the issue.
--&gt;
I can start up the celery worker normally, after which it will connect to the broker and begin to process tasks normally. When I go to run ctrl-c and perform a warm shutdown, the worker will start shutting down but then output a backtrace. This backtrace only occurs on this particular machine (Debian WSL environment running on windows 10).
'''
celery worker -A acdworker -l info
&lt;startup text&gt;
worker: Hitting Ctrl+C again will terminate all running tasks!

worker: Warm shutdown (MainProcess)
[2020-02-13 13:20:23,632: WARNING/MainProcess] Traceback (most recent call last):
[2020-02-13 13:20:23,633: WARNING/MainProcess] File &quot;/usr/lib/python3.7/multiprocessing/util.py&quot;, line 265, in _run_finalizers
    finalizer()
[2020-02-13 13:20:23,637: WARNING/MainProcess] File &quot;/usr/lib/python3.7/multiprocessing/util.py&quot;, line 189, in __call__
    res = self._callback(*self._args, **self._kwargs)
[2020-02-13 13:20:23,639: WARNING/MainProcess] File &quot;/home/austin/python_projects/acdid-automation/venv/lib/python3.7/site-packages/billiard/pool.py&quot;, line 1697, in _terminate_pool
    inqueue.close()
[2020-02-13 13:20:23,640: WARNING/MainProcess] AttributeError: 'NoneType' object has no attribute 'close'
'''"><pre class="notranslate"><code class="notranslate">
&lt;/p&gt;
&lt;/details&gt;

# Expected Behavior
&lt;!-- Describe in detail what you expect to happen --&gt;
After starting my worker instance using celery worker -A acdworker -l info, I should be able to perform a warm shutdown by doing ctrl-c.

'''
celery worker -A acdworker -l info
&lt;startup text&gt;
^C
worker: Hitting Ctrl+C again will terminate all running tasks!
worker: Warm shutdown (MainProcess)
'''
# Actual Behavior
&lt;!--
Describe in detail what actually happened.
Please include a backtrace and surround it with triple backticks (```).
In addition, include the Celery daemon logs, the broker logs,
the result backend logs and system logs below if they will help us debug
the issue.
--&gt;
I can start up the celery worker normally, after which it will connect to the broker and begin to process tasks normally. When I go to run ctrl-c and perform a warm shutdown, the worker will start shutting down but then output a backtrace. This backtrace only occurs on this particular machine (Debian WSL environment running on windows 10).
'''
celery worker -A acdworker -l info
&lt;startup text&gt;
worker: Hitting Ctrl+C again will terminate all running tasks!

worker: Warm shutdown (MainProcess)
[2020-02-13 13:20:23,632: WARNING/MainProcess] Traceback (most recent call last):
[2020-02-13 13:20:23,633: WARNING/MainProcess] File "/usr/lib/python3.7/multiprocessing/util.py", line 265, in _run_finalizers
    finalizer()
[2020-02-13 13:20:23,637: WARNING/MainProcess] File "/usr/lib/python3.7/multiprocessing/util.py", line 189, in __call__
    res = self._callback(*self._args, **self._kwargs)
[2020-02-13 13:20:23,639: WARNING/MainProcess] File "/home/austin/python_projects/acdid-automation/venv/lib/python3.7/site-packages/billiard/pool.py", line 1697, in _terminate_pool
    inqueue.close()
[2020-02-13 13:20:23,640: WARNING/MainProcess] AttributeError: 'NoneType' object has no attribute 'close'
'''
</code></pre></div></details>
<h1 dir="auto">Checklist</h1>
<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have read the relevant section in the<br>
<a href="http://docs.celeryproject.org/en/latest/contributing.html#other-bugs" rel="nofollow">contribution guide</a><br>
on reporting bugs.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have checked the <a href="https://github.com/celery/celery/issues?q=is%3Aissue+label%3A%22Issue+Type%3A+Bug+Report%22+-label%3A%22Category%3A+Documentation%22">issues list</a><br>
for similar or identical bug reports.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have checked the <a href="https://github.com/celery/celery/pulls?q=is%3Apr+label%3A%22PR+Type%3A+Bugfix%22+-label%3A%22Category%3A+Documentation%22">pull requests list</a><br>
for existing proposed fixes.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have checked the <a href="https://github.com/celery/celery/commits/master">commit log</a><br>
to find out if the bug was already fixed in the master branch.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have included all related issues and possible duplicate issues<br>
in this issue (If there are none, check this box anyway).</li>
</ul>
<h2 dir="auto">Mandatory Debugging Information</h2>
<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have included the output of <code class="notranslate">celery -A proj report</code> in the issue.<br>
(if you are not able to do this, then at least specify the Celery<br>
version affected).</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have verified that the issue exists against the <code class="notranslate">master</code> branch of Celery.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have included the contents of <code class="notranslate">pip freeze</code> in the issue.</li>
<li>[x I have included all the versions of all the external dependencies required<br>
to reproduce this bug.</li>
</ul>
<h2 dir="auto">Optional Debugging Information</h2>
<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue on more than one Python version<br>
and/or implementation.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue on more than one message broker and/or<br>
result backend.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue on more than one version of the message<br>
broker and/or result backend.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue on more than one operating system.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue on more than one workers pool.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue with autoscaling, retries,<br>
ETA/Countdown &amp; rate limits disabled.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> I have tried reproducing the issue after downgrading<br>
and/or upgrading Celery and its dependencies.</li>
</ul>
<h2 dir="auto">Environment &amp; Settings</h2>

<p dir="auto"><strong>Celery version</strong>: 4.4.0rc2 (cliffs)</p>

<details>
<summary><b><code class="notranslate">celery report</code> Output:</b></summary>
<p dir="auto">
</p><p dir="auto">software -&gt; celery:4.4.0rc2 (cliffs) kombu:4.6.3 py:3.7.3<br>
billiard:3.6.0.0 py-amqp:2.5.0<br>
platform -&gt; system:Linux arch:64bit<br>
kernel version:4.18.0-21-generic imp:CPython<br>
loader   -&gt; celery.loaders.app.AppLoader<br>
settings -&gt; transport:pyamqp results:redis://redis:6379/0</p>
<p dir="auto">broker_url: 'amqp://guest:********<a class="user-mention notranslate" data-hovercard-type="organization" data-hovercard-url="/orgs/rabbitmq/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://github.com/rabbitmq">@rabbitmq</a>:5672//'<br>
result_backend: 'redis://redis:6379/0'<br>
timezone: 'UTC'<br>
result_extended: True<br>
task_acks_late: True<br>
task_routes: {<br>
'celery.<em>': {'queue': 'api_workers'},<br>
'graphape.tasks.api.</em>': {'queue': 'api_workers'},<br>
'graphape.tasks.process.*': {'queue': 'process_workers'}}<br>
JOBTASTIC_CACHE: &lt;jobtastic.cache.base.WrappedCache object at 0x7f152c5ddb70&gt;<br>
redbeat_redis_url: 'redis://redis:6379/0'<br>
beat_schedule: {<br>
}</p>
<p dir="auto"></p>
</details>
<h1 dir="auto">Steps to Reproduce</h1>
<p dir="auto">Don't think anything other than celery 4.4.0RC and just having beat running and publishing a "celery.backend_cleanup"-task.<br>
Task in backend (redis) will have args set to null and this code will later try to enumerate from the null value:<br>
<a href="https://github.com/celery/celery/blob/master/celery/beat.py#L387">https://github.com/celery/celery/blob/master/celery/beat.py#L387</a></p>
<p dir="auto">I guess these lines should be patched to deal with args = null?<br>
Or perhaps args is never allowed to be null and fix should instead be already when task is written to backend?<br>
I'm not sure what celery specification says about null args, please advise.</p>
<h3 dir="auto">Python Packages</h3>

<details>
<summary><b><code class="notranslate">pip freeze</code> Output:</b></summary>
<p dir="auto">
alabaster==0.7.12
amqp==2.5.0
argcomplete==1.9.3
argh==0.26.2
asteval==0.9.14
Babel==2.7.0
billiard==3.6.0.0
bleach==3.1.0
boto3==1.9.179
botocore==1.12.179
bumpversion==0.5.3
cachelib==0.1
celery==4.4.0rc2
celery-redbeat==0.13.0
Cerberus==1.3.1
certifi==2019.6.16
cfn-flip==1.2.1
chardet==3.0.4
Click==7.0
coverage==4.5.3
decorator==4.4.0
dnspython==1.16.0
docutils==0.14
dumb-init==1.2.2
durationpy==0.5
Eve==0.9.2
eventlet==0.25.0
Events==0.3
Flask==1.0.3
Flask-SocketIO==4.1.0
future==0.16.0
graphape==0.0.1
greenlet==0.4.15
hjson==3.0.1
idna==2.8
imagesize==1.1.0
itsdangerous==1.1.0
Jinja2==2.10.1
jmespath==0.9.3
jobtastic==2.1.1
kappa==0.6.0
kombu==4.6.3
lambda-packages==0.20.0
livereload==2.6.1
MarkupSafe==1.1.1
mock==3.0.5
monotonic==1.5
networkx==2.3
numpy==1.16.4
packaging==19.0
pathtools==0.1.2
pkginfo==1.5.0.1
placebo==0.9.0
pluginbase==1.0.0
port-for==0.3.1
psutil==5.6.3
Pygments==2.4.2
pymongo==3.8.0
pyparsing==2.4.0
python-dateutil==2.6.1
python-engineio==3.8.1
python-slugify==1.2.4
python-socketio==4.1.0
pytz==2019.1
PyYAML==5.1.1
readme-renderer==24.0
redis==3.2.1
requests==2.22.0
requests-toolbelt==0.9.1
s3transfer==0.2.1
simplejson==3.16.0
six==1.12.0
snowballstemmer==1.2.1
Sphinx==2.0.1
sphinx-autobuild==0.7.1
sphinx-rtd-theme==0.4.3
sphinxcontrib-applehelp==1.0.1
sphinxcontrib-devhelp==1.0.1
sphinxcontrib-htmlhelp==1.0.2
sphinxcontrib-jsmath==1.0.1
sphinxcontrib-qthelp==1.0.2
sphinxcontrib-serializinghtml==1.1.3
tenacity==5.0.4
toml==0.10.0
tornado==6.0.2
tqdm==4.32.1
troposphere==2.4.9
twine==1.13.0
Unidecode==1.1.1
urllib3==1.25.3
uWSGI==2.0.18
vine==1.3.0
watchdog==0.9.0
webencodings==0.5.1
Werkzeug==0.15.4
wsgi-request-logger==0.4.6
zappa==0.48.2
</p>
</details>
<h3 dir="auto">Other Dependencies</h3>

<details>
<p dir="auto">
- celery-redbeat
</p>
</details>
<h1 dir="auto">Expected Behavior</h1>
<p dir="auto">No exception.</p>
<h1 dir="auto">Actual Behavior</h1>
<p dir="auto">Exception:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="[2019-07-02 04:00:00,081: ERROR/MainProcess] Message Error: Couldn't apply scheduled task celery.backend_cleanup: 'NoneType' object is not iterable
Traceback (most recent call last):
  File &quot;/usr/local/lib/python3.7/site-packages/celery/beat.py&quot;, line 387, in apply_async
    entry_args = [v() if isinstance(v, BeatLazyFunc) else v for v in entry.args]
TypeError: 'NoneType' object is not iterable

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File &quot;/usr/local/lib/python3.7/site-packages/redbeat/schedulers.py&quot;, line 427, in maybe_due
    result = self.apply_async(entry, **kwargs)
  File &quot;/usr/local/lib/python3.7/site-packages/celery/beat.py&quot;, line 400, in apply_async
    entry, exc=exc)), sys.exc_info()[2])
  File &quot;/usr/local/lib/python3.7/site-packages/vine/five.py&quot;, line 194, in reraise
    raise value.with_traceback(tb)
  File &quot;/usr/local/lib/python3.7/site-packages/celery/beat.py&quot;, line 387, in apply_async
    entry_args = [v() if isinstance(v, BeatLazyFunc) else v for v in entry.args]
celery.beat.SchedulingError: Couldn't apply scheduled task celery.backend_cleanup: 'NoneType' object is not iterable"><pre class="notranslate"><code class="notranslate">[2019-07-02 04:00:00,081: ERROR/MainProcess] Message Error: Couldn't apply scheduled task celery.backend_cleanup: 'NoneType' object is not iterable
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/celery/beat.py", line 387, in apply_async
    entry_args = [v() if isinstance(v, BeatLazyFunc) else v for v in entry.args]
TypeError: 'NoneType' object is not iterable

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/redbeat/schedulers.py", line 427, in maybe_due
    result = self.apply_async(entry, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/celery/beat.py", line 400, in apply_async
    entry, exc=exc)), sys.exc_info()[2])
  File "/usr/local/lib/python3.7/site-packages/vine/five.py", line 194, in reraise
    raise value.with_traceback(tb)
  File "/usr/local/lib/python3.7/site-packages/celery/beat.py", line 387, in apply_async
    entry_args = [v() if isinstance(v, BeatLazyFunc) else v for v in entry.args]
celery.beat.SchedulingError: Couldn't apply scheduled task celery.backend_cleanup: 'NoneType' object is not iterable
</code></pre></div>