Does anyone know what Heroku changes on deploy? I've got a local dev machine setup with Ubuntu 11.10, and my project installed into a venv, all packages managed via pip. The corresponding requirements.txt is in my repo, and is sent to Heroku on push. Both my local machine and Heroku are accessing the same RDS instance on AWS.

Running the Django dev server locally (manage.py runserver) results in a working page. Attempting to run (via my Procfile) the dev server on Heroku causes an error in the template at {% url foobar %} as follows: 

```
Caught TypeError while rendering: 'ParseResult' object is not callable

```

My requirements.txt contains the following:

```
Django==1.3.1
MySQL-python==1.2.3
PIL==1.1.7
amqplib==1.0.2
anyjson==0.3.1
boto==2.2.2
celery==2.5.1
distribute==0.6.24
django-celery==2.5.1
django-kombu==0.9.4
django-picklefield==0.2.0
django-piston==0.2.3
gevent==0.13.6
greenlet==0.3.4
gunicorn==0.14.2
httplib2==0.7.4
kombu==2.1.1
python-dateutil==1.5
wsgiref==0.1.2
zencoder==0.4

```

Anyone have an idea?