Bugfix in connection_for method

src/packetserver/client/__init__.py

@@ -40,7 +40,7 @@ class Client:
         if not ax25.Address.valid_call(callsign):
             raise ValueError("Must supply a valid callsign.")
         callsign = callsign.upper().strip()
-        for key in self.connections:
+        for key in self.connections.keys():
             if key.split(1) == callsign:
                 return self.connections['key']
         return self.new_connection(callsign)