Make less file system access to the cache.

theano/gof/cmodule.py

@@ -640,13 +640,16 @@ class ModuleCache(object):
             time_now = time.time()
             # Go through directories in alphabetical order to ensure consistent
             # behavior.
-            root_dirs_files = sorted(os.walk(self.dirname),
-                                     key=operator.itemgetter(0))
-            for root, dirs, files in root_dirs_files:
+            subdirs = sorted(os.listdir(self.dirname))
+            for root in subdirs:
+                root = os.path.join(self.dirname, root)
                 key_pkl = os.path.join(root, 'key.pkl')
                 if key_pkl in self.loaded_key_pkl:
                     continue
-                elif 'delete.me' in files or not files:
+                if not os.path.isdir(root):
+                    continue
+                files = os.listdir(root)
+                if 'delete.me' in files or not files:
                     _rmtree(root, ignore_nocleanup=True,
                             msg="delete.me found in dir")
                 elif 'key.pkl' in files:
@@ -814,8 +817,7 @@ class ModuleCache(object):
                 # We do nothing here.
 
             # Clean up the name space to prevent bug.
-            if root_dirs_files:
-                del root, dirs, files
+            del root, files, subdirs
 
             # Remove entries that are not in the filesystem.
             items_copy = list(self.module_hash_to_key_data.iteritems())