py3: make doc strings containing deprecated '\.' escape sequence raw strings stable

py3: make doc strings containing deprecated '\.' escape sequence raw strings

Differential Revision: https://phab.mercurial-scm.org/D7462

--- a/mercurial/match.py	Tue Nov 19 14:59:23 2019 -0500
+++ b/mercurial/match.py	Wed Nov 20 19:16:11 2019 -0800
@@ -554,7 +554,7 @@
 
 
 class patternmatcher(basematcher):
-    """Matches a set of (kind, pat, source) against a 'root' directory.
+    r"""Matches a set of (kind, pat, source) against a 'root' directory.
 
     >>> kindpats = [
     ...     (b're', br'.*\.c$', b''),
@@ -1172,7 +1172,7 @@
 
 
 def patkind(pattern, default=None):
-    '''If pattern is 'kind:pat' with a known kind, return kind.
+    r'''If pattern is 'kind:pat' with a known kind, return kind.
 
     >>> patkind(br're:.*\.c$')
     're'