fixup! test_json_schema: resolve `request` and `response` schemas

use six for python3 compatibility

slapos/test/test_json_schema.py

@@ -25,14 +25,16 @@
 #
 ##############################################################################
 
-import unittest
-import os
+import collections
 import glob
 import json
-import collections
-import slapos.test
+import os
+import unittest
+
 import jsonschema
+import six
 
+import slapos.test
 
 def createInstanceParameterSchemaValidatorTest(path):
   # Test that json is a valid json schema, supports several
@@ -65,7 +67,7 @@ def createSoftwareCfgValidatorTest(path, software_cfg_schema):
       # also make sure request and response schemas can be resolved
       schema.setdefault('$id', 'file://' + path)
       resolver = jsonschema.RefResolver.from_schema(schema)
-      for software_type_definition in schema['software-type'].itervalues():
+      for software_type_definition in six.itervalues(schema['software-type']):
         resolver.resolve(software_type_definition['request'])
         resolver.resolve(software_type_definition['response'])