Remove six usage

This repo does not support Python 2 anymore, so we don't need
six for compatibility between Python2 and 3, convert six usage to Python
3 code.

Note that six.text_type is "str" in Python 3, so we can remove the
clause completly.

Needed-By: https://review.opendev.org/701743
Change-Id: I7dbdf7b773d72db9204c6251b1ce561cf7675522

magnum_ui/api/magnum.py

@@ -15,7 +15,6 @@
 
 from __future__ import absolute_import
 import logging
-import six
 
 from django.conf import settings
 
@@ -52,7 +51,7 @@ def _cleanup_params(attrs, create, **params):
             raise exceptions.BadRequest(
                 "Key must be in %s" % ",".join(attrs))
         if key == "labels":
-            if isinstance(value, str) or isinstance(value, six.text_type):
+            if isinstance(value, str):
                 labels = {}
                 vals = value.split(",")
                 for v in vals: