Bug#782277: please check for mismatches in python dependencies

[Matthias Klose <doko@debian.org>]

Package: lintian

Please could lintian check for mismatches in python dependencies, in that a
python module depends on python3 modules or the other way around?

  Package: python3-foo
  Depends: python-gi, python-gi-dev

So here it should be python3-gi, but python-gi-dev is correct, and there are
probably other exceptions like python-foo-common dependencies.

Such a warning/error would be helpful before starting to convert to python3 for
applications and packages.

Also a warning would be good for dependencies on both python and python3. These
are mostly wrong for most packages.