Bug#902582: (some kind of) transition: add python3.7 as a supported python3 version

[Matthias Klose <doko@debian.org>]

Package: release.debian.org
Severity: normal
User: release.debian.org@packages.debian.org
Usertags: transition

Please setup a tracker to add python3.7 as a supported python3 version. This is 
non-blocking, as packages can migrate on their own once built.

is_affected = .build-depends ~ /python3-all-dev/;
is_good = .depends ~ /python3 \(<< 3\.8\)/ | .depends ~ /python3.7/;
is_bad = .depends ~ /python3 \(<< 3\.7\)/ | .breaks ~ /python \(>= 3\.7\)/;