--- a/server/python/junius/pipeline.py
+++ b/server/python/junius/pipeline.py
@@ -35,53 +35,53 @@ class Pipeline(object):
                 self.forward_chain[from_type] = (to_type, inst)
 
     def start(self):
         return defer.maybeDeferred(self.process_all_documents
                     ).addCallback(self._cb_maybe_reprocess_all_documents)
 
     def process_all_documents(self):
         # check *every* doc in the DB.  This exists until we can derive
-        # a workqueue based on views.\
+        # a workqueue based on views.
         self.num_this_process = 0
         return self.doc_model.db.openView('raindrop!messages!by',
                                           'by_doc_roots',
                                           group=True, limit=100,
                     ).addCallback(self._cb_roots_opened)
 
     def _cb_maybe_reprocess_all_documents(self, result):
-        if self.num_this_process != 0:
+        if self.num_this_process:
             logger.debug('pipeline processed %d documents last time; trying again',
                          self.num_this_process)
             return self.start()
         logger.info('pipeline is finished.')
 
     def _cb_roots_opened(self, rows):
         dl = []
         for row in rows:
             did = row['key']
-            logger.debug("Finding last extention point for %s", did)
+            logger.debug("Finding last extension point for %s", did)
             dl.append(
                 self.doc_model.get_last_ext_for_document(did).addCallback(
                     self._cb_got_doc_last_ext, did)
                 )
         return defer.DeferredList(dl)
 
     def _cb_got_doc_last_ext(self, ext_info, rootdocid):
         last_ext, docid = ext_info
         if last_ext is None:
-            logger.debug("Document '%s' doesn't appear to be a message; skipping",
-                        rootdocid)
-            return
+            logger.debug("Document '%s' doesn't appear to be a message; skipping",
+                         rootdocid)
+            return None
         try:
             xform_info = self.forward_chain[last_ext]
         except KeyError:
             logger.warning("Can't find transformer for message type %r - skipping %r",
                            last_ext, docid)
-            return
+            return None
         logger.debug("Last extension for doc '%s' is '%s'", docid, last_ext)
         return self.doc_model.open_document(docid
                     ).addCallback(self._cb_got_last_doc, rootdocid, xform_info
                     )
 
     def _cb_got_last_doc(self, doc, rootdocid, xform_info):
         assert doc is not None, "failed to locate the doc for %r" % rootdocid
         dest_type, xformer = xform_info