py3: fix bad escapes of sub() replacement pattern in test-template-basic.t
Python 3.7 starts complaining about it. We have to double the backslash or
'\x5c' to get around.
Georges Racinet <gracinet@anybox.fr> [Thu, 13 Dec 2018 17:10:03 +0100] rev 40954
perfdiscovery: benching findcommonheads()
This works between the local repo and any peer given by its path, and
should be useful for further work on discovery
Differential Revision: https://phab.mercurial-scm.org/D5418