Clean old cruft, provide pythonX.Y
In diff order:
- gdbm releases in all Fedoras are long above 1:1.13
- the flat package should be called python3.7 but we are lazy to rename
- system-python is long gone, upgrade path works
- python3-enum34 is only required by 2 pkgs [0][1]
- glibc releases in all Fedoras are long above 2.24.90-26
Not removed:
- platform-python obsoletes shall be removed in Fedora 31, they were added in 28
[0] https://src.fedoraproject.org/rpms/python-qt5/pull-request/3
[1] https://src.fedoraproject.org/rpms/python-taskflow/pull-request/1