Fix a function in rpn plugin to reply with error

plugins/rpn.py

@@ -55,7 +55,8 @@ class rpn(object):
                         elif char == "/":
                             self.stack.append(b / a)
                     except Exception as e:
-                        self.conn.reply(str(e))
+                        # Hardcoding this bit in many places is stupid.
+                        self.server.doMessage(channel, user + ": " + str(e))
                         return
             try:
                 self.server.doMessage(channel, user + ": " + str(self.stack[0]))