tests: fix up some lax escaping in test-template-basic.t...
tests: fix up some lax escaping in test-template-basic.t
These misfired escapes turn into hard errors in Python 3.7, and I'd
really rather we not work around it. We should *probably* try and find
a way to proactively warn users about invalid escape sequences.
There's one more failure of this type in this file on Python 3.7, but
I can't figure out the issue. It'll need to be corrected in a
follow-up.
Differential Revision:
https://phab.mercurial-scm.org/D3843
