Catch harmless error seen in apache logs during shutdown

nilmdb/fsck/fsck.py

@@ -59,6 +59,8 @@ def retry_if_raised(exc, message = None, max_retries = 100):
 
 class Progress(object):
     def __init__(self, maxval):
+        if maxval == 0:
+            maxval = 1
         self.bar = progressbar.ProgressBar(
             maxval = maxval,
             widgets = [ progressbar.Percentage(), ' ',

nilmdb/utils/serializer.py

@@ -117,7 +117,10 @@ def serializer_proxy(obj_or_type):
             return ret
 
         def __del__(self):
-            self.__call_queue.put((None, None, None, None))
+            try:
-            self.__thread.join()
+                self.__call_queue.put((None, None, None, None))
+                self.__thread.join()
+            except TypeError: # pragma: no cover
+                pass
 
     return SerializerObjectProxy(obj_or_type)