pdgmail should get rid of Python 2 and use Python 3 only

Python 2.x will no longer be supported by their upstream developers in 2020. Thus Debian developers are actively removing Python 2 support in Debian Testing with the goal of getting rid of Python 2 in Debian 11 (bullseye). We must do the same as our packages relying on Python 2 modules provided by Debian will start to break...

pdgmail depends on Python 2.x and needs to be reviewed. Applications have to switch to Python 3. Python modules have to stop providing packages for Python 2 (as soon as no other packages depend on the Python 2 version of the module).

In any case, this work must be done in coordination with upstream. Tag the issue with ~Forwarded once you have opened an upstream issue requesting this.

If the package can't be fixed currently, then tag the bug with ~Blocked and add the issues of the blocking packages as “Related issues”.