Broken backward compatibility: missing **playhouse.shortcuts.RetryOperationalError**
I don't see it in the documentation, it's been removed. My old code run on peewee 3.1.5 raise ImportError: cannot import name RetryOperationalError
how to use RetryOperationalError on 3.1.5, the docs can't find anything about it It was removed in 3.0.
```
  File "/home/rcir178/NZ-ORCID-Hub/orcid_hub/__init__.py", line 28, in <module>
    from playhouse.shortcuts import RetryOperationalError
ImportError: cannot import name 'RetryOperationalError'
ERROR: could not load /home/rcir178/NZ-ORCID-Hub/tests/conftest.py
```

The documentation still refers to it: 