Revert "Use openssl via m2crypto for digests instead of hashlib"

This reverts commit 4278d679524dd0d2720e346003732086a69cd3e5.

Use the backported python-hashlib for hash functions instead of M2Crypto.
Switch to the old yum callbacks

procReqPo and procConflictPo don't exist yet because this is the past.

(TARDIS NOISES)
Oldenated the string format operations.

str.format was added in Python 2.6