Fix unable to start Medusa due to configparser ImportError

[sharkykh]

Fixes #5137

I had a hunch that the .pth file I got when installing the package locally was important.
I can try to explain the fix better later, if anyone is interested, but basically site.addsitedir adds a path to sys.path, plus it handles these files if any are found on the path.
However it uses appends and not insert, that's why we need to rebuild sys.path like in the new code.

https://bugs.python.org/issue7744

[hobeone]

This doesn't seem to work if you have configparser installed with a system package:

Traceback (most recent call last):
  File "/opt/medusa/start.py", line 6, in <module>
    from medusa.__main__ import main
  File "/opt/medusa/medusa/__main__.py", line 67, in <module>
    from medusa import (
  File "/opt/medusa/medusa/name_cache.py", line 12, in <module>
    from medusa.scene_exceptions import (
  File "/opt/medusa/medusa/scene_exceptions.py", line 13, in <module>
    import adba
  File "/opt/medusa/ext/adba/__init__.py", line 27, in <module>
    from configparser import ConfigParser
  File "/opt/medusa/ext/configparser.py", line 12, in <module>
    from backports.configparser import (
ImportError: cannot import name ConverterMapping

After running apt-get remove python-configparser medusa starts as normal.

This is on Debian testing. I ran git reset --hard origin/master to make sure everything was up to date but removing the system package was the only thing that got it working.

Debian package info:

Package: python-configparser
Source: configparser
Version: 3.5.0b2-1

[sharkykh]

@hobeone
Unfortunately I don't have a way of testing this, but can you try re-adding this file:
https://github.com/pymedusa/Medusa/raw/31171bc896108a52f80cfd90f3c70f0baf205db2/ext/backports/__init__.py
Save it to /opt/medusa/ext/backports/__init__.py
Reinstall the python-configparser system package and try to run medusa.

[sharkykh]

Also I must say,
that debian package seems to be out of date with the actual library version and that's probably the reason for the issue: Current library version is 3.5.0 (it's out of beta) - 3.5.0b2 is from 2014.
If you still want to use the system package over installing a user package with pip,
I suggest contacting the debian pkg maintainer(s) to bump the version.
https://packages.debian.org/sid/python-configparser

[hobeone]

Adding that init.py file doesn't seem to fix it. I get the same error code when starting.

I think you're right about the package being too old. When I get a second I'll see about filing a request to update it.