(PUP-1362) (PUP-1775) remove :python command

No longer needed after removal of yumhelper.py
(PUP-1362) (PUP-1775) map yumhelper.py's -e & -d flags to yum

The -e & -d flags to yumhelper.py had different semantics than yum's -d & -e
flags.  The yum equivalent option flags are --enablerepo & --disablerepo.
Merge remote-tracking branch 'upstream/pr/3335'

* upstream/pr/3335:
  (PUP-1362) (PUP-1775) map yumhelper.py's -e & -d flags to yum
  (PUP-1362) (PUP-1775) remove :python command