util: rename a variable to avoid confusing pytype

Fixes the following warning:

   line 1205, in f: No attribute 'append' on Dict[nothing, nothing] [attribute-error]
         In Union[Dict[nothing, nothing], list]

Differential Revision: https://phab.mercurial-scm.org/D7673

mercurial/util.py

@@ -1195,12 +1195,12 b' def cachefunc(func):'
     '''cache the result of function calls'''
     # XXX doesn't handle keywords args
     if func.__code__.co_argcount == 0:
-        cache = []
+        listcache = []
 
         def f():
-            if len(cache) == 0:
-                cache.append(func())
-            return cache[0]
+            if len(listcache) == 0:
+                listcache.append(func())
+            return listcache[0]
 
         return f
     cache = {}