convert: change socket mode from b'r+' to 'rwb' in cvs.py (issue6789)
'r+' mode used to open sockets for read/write operations, but '+' is not
supported in Python 3. We're using bytes with these sockets everywhere, so the
mode should have 'b'. But the mode argument has to be str, not bytes.
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init repo
$ cd repo
$ echo 'base' > base
$ hg ci -Ambase
adding base
$ hg qnew -mmqbase mqbase
$ hg qsave
$ hg qrestore 2
restoring status: hg patches saved state