fix StringType and itervalues in plugin and cli

cli/koji

@@ -51,7 +51,7 @@ def register_plugin(plugin):
 
     Handlers are functions marked with one of the decorators defined in koji.plugin
     """
-    for v in vars(plugin).itervalues():
+    for v in six.itervalues(vars(plugin)):
         if isinstance(v, (types.ClassType, types.TypeType)):
             #skip classes
             continue

koji/plugin.py

@@ -24,6 +24,7 @@ import koji
 import logging
 import sys
 import traceback
+import six
 
 # the available callback hooks and a list
 # of functions to be called for each event
@@ -91,7 +92,7 @@ class PluginTracker(object):
         return self.plugins.get(name)
 
     def pathlist(self, path):
-        if isinstance(path, basestring):
+        if isinstance(path, six.string_types):
             return [path]
         else:
             return path