patch: update copying of dict keys and values to work on Python 3 stable

patch: update copying of dict keys and values to work on Python 3

--- a/mercurial/patch.py	Fri Jul 21 14:22:08 2017 +0000
+++ b/mercurial/patch.py	Mon Jul 24 14:42:55 2017 -0400
@@ -2569,7 +2569,7 @@
 
     if relroot != '' and (repo.ui.configbool('devel', 'all-warnings')
                           or repo.ui.configbool('devel', 'check-relroot')):
-        for f in modified + added + removed + copy.keys() + copy.values():
+        for f in modified + added + removed + list(copy) + list(copy.values()):
             if f is not None and not f.startswith(relroot):
                 raise AssertionError(
                     "file %s doesn't start with relroot %s" % (f, relroot))