Fixing two bugs related to approval

* If roles not present in keystone, we throw and error
  while trying to handle an error.
* when data is empty we fail to return a useful error message.

Change-Id: I8572cf7ce35997cd7b5a38658a3e4eb26afe4941

stacktask/actions/v1/base.py

@@ -289,7 +289,7 @@ class UserMixin(ResourceMixin):
         except Exception as e:
             self.add_note(
                 "Error: '%s' while %s the roles: %s on user: %s " %
-                (e, action_string, self.roles, user))
+                (e, action_string, roles, user))
             raise
 
     def enable_user(self, user=None):

stacktask/api/v1/views.py

@@ -18,6 +18,7 @@ from django.conf import settings
 from django.utils import timezone
 from django.core.paginator import Paginator, EmptyPage, PageNotAnInteger
 
+from rest_framework.exceptions import ParseError
 from rest_framework.response import Response
 from rest_framework.views import APIView
 
@@ -350,10 +351,15 @@ class TaskDetail(APIViewWithLogger):
                 {'errors': ['No task with this id.']},
                 status=404)
 
+        try:
             if request.data.get('approved') is not True:
                 return Response(
                     {'approved': ["this is a required boolean field."]},
                     status=400)
+        except ParseError:
+            return Response(
+                {'approved': ["this is a required boolean field."]},
+                status=400)
 
         if task.completed:
             return Response(