py3: invalidate repository cache with system-string keys

# skip-blame just a few r'' prefixes

hgext/mq.py

@@ -3511,9 +3511,9 b' def reposetup(ui, repo):'
 
         def invalidateall(self):
             super(mqrepo, self).invalidateall()
-            if localrepo.hasunfilteredcache(self, 'mq'):
+            if localrepo.hasunfilteredcache(self, r'mq'):
                 # recreate mq in case queue path was changed
-                delattr(self.unfiltered(), 'mq')
+                delattr(self.unfiltered(), r'mq')
 
         def abortifwdirpatched(self, errmsg, force=False):
             if self.mq.applied and self.mq.checkapplied and not force:

mercurial/localrepo.py

@@ -2047,9 +2047,9 b' class localrepository(object):'
 
     def invalidatecaches(self):
 
-        if '_tagscache' in vars(self):
+        if r'_tagscache' in vars(self):
             # can't use delattr on proxy
-            del self.__dict__['_tagscache']
+            del self.__dict__[r'_tagscache']
 
         self.unfiltered()._branchcaches.clear()
         self.invalidatevolatilesets()