few flake8 and python3 problems corrected

cas_server/models.py

@@ -18,7 +18,6 @@ from django.contrib import messages
 from django.utils.translation import ugettext_lazy as _
 from django.utils import timezone
 from django.utils.encoding import python_2_unicode_compatible
-from django.core.exceptions import ValidationError
 from django.core.mail import send_mail
 
 import re

cas_server/tests/test_models.py

@@ -81,6 +81,7 @@ class FederatedUserTestCase(TestCase, UserModels, FederatedIendityProviderModel)
         self.assertIsNone(user._attributs)
         self.assertIsNone(user.attributs)
 
+
 class FederateSLOTestCase(TestCase, UserModels):
     """test for the federated SLO model"""
     def test_clean_deleted_sessions(self):

cas_server/tests/utils.py

@@ -16,10 +16,6 @@ import django
 from django.test import Client
 from django.template import loader
 from django.utils import timezone
-if django.VERSION < (1, 8):
-    from django.template import Context
-else:
-    Context = lambda x:x
 
 import cgi
 import six
@@ -33,6 +29,13 @@ from cas_server import models
 from cas_server import utils
 
 
+if django.VERSION < (1, 8):
+    from django.template import Context
+else:
+    def Context(arg):
+        return arg
+
+
 def return_unicode(string, charset):
     """make `string` a unicode if `string` is a unicode or bytes encoded with `charset`"""
     if not isinstance(string, six.text_type):

cas_server/utils.py

@@ -654,8 +654,8 @@ def last_version():
     else:
         try:
             req = requests.get(settings.CAS_NEW_VERSION_JSON_URL)
-            data = json.loads(req.content)
+            data = json.loads(req.text)
-            versions = data["releases"].keys()
+            versions = list(data["releases"].keys())
             versions.sort()
             version = versions[-1]
             last_version._cache = (time.time(), version, True)