py3: use email.utils module instead of email.Utils
On py2:
>>> import email
>>> import email.utils as eutil
>>> email.Utils.parseaddr is eutil.parseaddr
True
>>> email.Utils.formatdate is eutil.formatdate
True
email.Utils is not present on Python 3.
Differential Revision: https://phab.mercurial-scm.org/D2453
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init
$ echo 'base' > base
$ hg ci -Ambase
adding base
$ hg qnew -mmqbase mqbase
$ hg qsave
$ hg qrestore 2
restoring status: hg patches saved state