This updates all Python packages that download their source from PyPi to
use pypi.mk.

This will allow future improvements/changes to pypi.mk to affect all
relevant packages.

This also makes it easier for future Python packages to start using
pypi.mk, when it's clear how it is used in existing packages.

Signed-off-by: Jeffery To <jeffery.to@gmail.com>

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

After many failed attempts at upgrading Django to 2.2.6, the solution seems
to be to split a `python-django1` package that works with Python2 and
upgrade `python3-django` to the latest 2.2[.6] LTS release.

This also means that all Python2 Django packages will be stuck & based on
Django 1.11[.24] LTS release. But, it's currently the sanest approach I
could find to be able to perform an upgrade of Django to 2.2, and not break
Seafile.

Upgrading Seafile is also pretty difficult, as their Python3 support is not
yet finished & released. And in the meantime, we want to allow people to
use newer Django versions.

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>