Weblate 2.19.1 depends on "Python Social Auth - Core" which is not packaged for Debian

Info:

• Weblate 2.19.1 depends on Python Social Auth - Core (pypi) >= 1.3.0.
• Latest version packaged for debian is python-social-auth 1:0.2.21+dfsg-1.
• In December 2016 the initial pypi package was deprecated, in favour of split new ones. The package in debian corresponds to the old organization of the code.
• 1:0.2.21+dfsg-1 was uploaded to Debian in January 2017. It was removed from testing in January 2018 (because of a paradox involving a css file).
• There's a RFP for python social auth in Debian bug tracker.

Python Social Auth - Core depends on:

• requests>=2.9.1 (2.12.4-1 is in stretch: py2, py3) (ok)
• oauthlib>=1.0.3 (2.0.1-1 is in stretch: py2, py3) (ok)
• requests-oauthlib>=0.6.1 (0.7.0-0.1 is in stretch: py2, py3) (ok)
• six>=1.10.0 (1.10.0-3 is in stretch: py2, py3) (ok)
• PyJWT>=1.4.0 (1.4.2-1+deb9u1 is in stretch: py2, py3) (ok)
• python-openid>=2.2.5 (py2 only, 2.2.5-6 is in stretch: py2 (ok)
• python-openid>=3.0.10 (py3 only, 3.0.9-1 is in sid: py3 (needs update)
• defusedxml>=0.5.0rc1 (py3 only, 0.5.0-1 is in stretch: py3) (ok)

Initial tasks could be:

• Contact the packagers of python-social-auth and the packagers of python3-openid and ask them if they have plans for an upgrade.
• Create a new package python-social-auth-core for Python 2 only. Add Python 3 afterwards.

Dismissed ideas:

• Check with Weblate dev if python-social-auth is strictly needed for functioning of Weblate. Maybe we can just patch something out. - We have decided to just do the packaging instead