py3: add a r'' prefix in mercurial/exchange.py

# skip-blame because just r'' prefix

This fixes test-narrow-acl.t on py3 which was broken by one of the
earlier patches.

Differential Revision: https://phab.mercurial-scm.org/D5149

mercurial/exchange.py

@@ -2170,7 +2170,7 b' def _getbundlechangegrouppart(bundler, r'
     if 'treemanifest' in repo.requirements:
         part.addparam('treemanifest', '1')
 
-    if (kwargs.get(r'narrow', False) and kwargs.get('narrow_acl', False)
+    if (kwargs.get(r'narrow', False) and kwargs.get(r'narrow_acl', False)
         and (include or exclude)):
         narrowspecpart = bundler.newpart('narrow:spec')
         if include: