Fix syntax error in Python 2

pyrcb.py

@@ -333,7 +333,7 @@ class IRCBot(object):
     def _on_005_isupport(self, server, target, *args):
         for arg in args[:-1]:
-            name, value, *_ = arg.split("=", 1) + [None]
+            name, value = (arg.split("=", 1) + [None])[:2]
             if name == "PREFIX":
                 modes, prefixes = value[1:].split(")", 1)
                 self._prefix_map = dict(zip(modes, prefixes))