fixed some problems with admin no GAE, still readonly

gluon/cfs.py

@@ -14,6 +14,7 @@ FOR INTERNAL USE ONLY
 
 import os
 import thread
+import logging
 from fileutils import read_file
 
 cfs = {}  # for speed-up
@@ -34,15 +35,16 @@ def getcfs(key, filename, filter=None):
     This is used on Google App Engine since pyc files cannot be saved.
     """
     try:
+        logging.info(filename)
         t = os.stat(filename).st_mtime
     except OSError:
-        return filter()
+        return filter() if callable(filter) else ''
     cfs_lock.acquire()
     item = cfs.get(key, None)
     cfs_lock.release()
     if item and item[0] == t:
         return item[1]
-    if not filter:
+    if not callable(filter):
         data = read_file(filename)
     else:
         data = filter()