Fix a couple of python bugs

synapse/federation/federation_client.py

@@ -236,9 +236,9 @@ class FederationClient(FederationBase):
         # TODO: Rate limit the number of times we try and get the same event.
 
         if self._get_pdu_cache:
-            e = self._get_pdu_cache.get(event_id)
-            if e:
-                defer.returnValue(e)
+            ev = self._get_pdu_cache.get(event_id)
+            if ev:
+                defer.returnValue(ev)
 
         pdu = None
         for destination in destinations:
@@ -269,7 +269,7 @@ class FederationClient(FederationBase):
 
                         break
 
-            except SynapseError:
+            except SynapseError as e:
                 logger.info(
                     "Failed to get PDU %s from %s because %s",
                     event_id, destination, e,
@@ -336,8 +336,10 @@ class FederationClient(FederationBase):
                 ev.event_id: ev for ev in fetched_events
             }
 
-            pdus = [event_map[e_id] for e_id in state_event_ids]
-            auth_chain = [event_map[e_id] for e_id in auth_event_ids]
+            pdus = [event_map[e_id] for e_id in state_event_ids if e_id in event_map]
+            auth_chain = [
+                event_map[e_id] for e_id in auth_event_ids if e_id in event_map
+            ]
 
             auth_chain.sort(key=lambda e: e.depth)