fix_bytesmod: fix defects in fix_bytesmod so it produces working code
Prior to this change, the fixer did not always add the py3kcompat
import to files, and did not manage to blacklist itself.
discovery: improve "note: unsynced remote changes!" warning
This note (which actually is a warning) frequently caused confusion.
"unsynced" is not a well established user-facing concept in Mercurial and the
message was not very specific or helpful.
Instead, show a messages like:
remote has heads on branch 'default' that are not known locally:
6c0482d977a3
and show it before aborting on "push creates new remote head". This will also
give more of a hint in the case where the branch has been closed remotely and
'hg heads' thus not would show any new heads after pulling.
A similar (but actually very different) message was addressed in
6b618aa08b6e.