Intent to orphan Python 2

[Petr Viktorin]

tl;dr: Unless someone steps up to maintain Python 2 after 2020, we need 
to start dropping python2 packages now.


Python 2.7 will reach end of upstream support on 1st of January, 2020, 
after almost 10 years (!) of volunteer maintenance.

Fedora still has more than 3000 packages depending on python2 – many 
more than we can support without upstream help.
We (rightly) don't have the authority to say "please drop your unneeded 
python2 subpackages, or let us drop them for you" [0].
The next best thing we *can* say is: "if Fedora is to keep python2 
alive, we won't be the ones doing it – at least not at the current 
magnitude".
Here are the details.


The current maintainers of python2 would like to "orphan" the python2 
package in 2020 (~ Fedora 30):
- Charalampos Stratakis (cstratak)
- Tomáš Orsava (torsava)
- Miro Hrnočok (churchyard)
- Petr Viktorin (pviktori)
- Iryna Schcherbina (ishcherb)
- Michal Cyprian (mcyprian)
- Bohuslav Kabrda (bkabrda)
- David Malcolm (dmalcolm)
- Thomas Spura (tomspur)

As with any orphaning, that leaves two options:
- someone else agrees now to take over in 2020 (keeping in mind this is 
a security-critical package and will be abandoned upstream), or
- dependent packages drop support for Python 2.

Unlike most other orphanings, we have some thousands of dependent 
packages, so a lot of time and care is required.
In case no one steps up, we'd like to start dropping Python 2 support 
from dependent packages *now*, starting with ported libraries on whose 
python2 version nothing in Fedora depends. (We keep a list of those at [1].)
Of course, we're ready to make various compromises with interested 
packagers, as long as there's an understanding that we won't just 
support python2 forever.

If you are a maintainer of anything at [1] we ask you kindly to consider 
removing the python2 subpackages.
You can either do it now in Rawhide, or add a conditional for Fedora > 
29. (On the current schedule, Fedora 30 will be the first release still 
supported after 2020-01-01.)

If no one steps up to maintain python2 after 2020, we're prepared to 
package a "legacy" python27 package, similar to what we do for e.g. 
python33 [2], to:
- help developers that still need to test against this version
- support exceptionally important non–security critical applications, if 
their upstreams don't manage to port to Python 3 in time



[0] https://pagure.io/packaging-committee/issue/753
[1] http://fedora.portingdb.xyz/#legacy-leaf
[2] https://src.fedoraproject.org/rpms/python33/