Irc: add getFriendlyName() abstraction

Closes #260.

classes.py

@@ -871,6 +871,16 @@ class Irc():
 
         return '%s!%s@%s' % (nick, ident, host)
 
+    def getFriendlyName(self, entityid):
+        """
+        Returns the friendly name of a SID or UID (server name for SIDs, nick for UID)."""
+        if entityid in self.servers:
+            return self.servers[entityid].name
+        elif entityid in self.users:
+            return self.users[entityid].nick
+        else:
+            raise KeyError("Unknown UID/SID %s" % entityid)
+
     def isOper(self, uid, allowAuthed=True, allowOper=True):
         """
         Returns whether the given user has operator status on PyLink. This can be achieved

protocols/ircs2s_common.py

@@ -24,13 +24,10 @@ class IRCS2SProtocol(Protocol):
         # What we actually want is to format a pretty kill message, in the form
         # "Killed (killername (reason))".
 
-        if source in self.irc.users:
-            # Killer was a user (they're SO fired)
-            killer = self.irc.users[source].nick
-        elif source in self.irc.servers:
-            # Killer was a server (impossible, the machine is always right)
-            killer = self.irc.servers[source].name
-        else:
+        try:
+            # Get the nick or server name of the caller.
+            killer = self.irc.getFriendlyName(source)
+        except KeyError:
             # Killer was... neither? We must have aliens or something. Fallback
             # to the given "UID".
             killer = source