E2E key query: handle federation fails

Don't fail the whole request if we can't connect to a particular server.

synapse/handlers/e2e_keys.py

@@ -16,6 +16,7 @@
 import ujson as json
 import logging
 
+import twisted.internet.error
 from canonicaljson import encode_canonical_json
 from twisted.internet import defer
 
@@ -111,6 +112,11 @@ class E2eKeysHandler(object):
                 failures[destination] = {
                     "status": 503, "message": "Not ready for retry",
                 }
+            except Exception as e:
+                # include ConnectionRefused and other errors
+                failures[destination] = {
+                    "status": 503, "message": e.message
+                }
 
         yield preserve_context_over_deferred(defer.gatherResults([
             preserve_fn(do_remote_query)(destination)
@@ -222,6 +228,11 @@ class E2eKeysHandler(object):
                 failures[destination] = {
                     "status": 503, "message": "Not ready for retry",
                 }
+            except Exception as e:
+                # include ConnectionRefused and other errors
+                failures[destination] = {
+                    "status": 503, "message": e.message
+                }
 
         yield preserve_context_over_deferred(defer.gatherResults([
             preserve_fn(claim_client_keys)(destination)