Integrate a migration-detector middleware

This attempts to detect if there are migrations in-progress and will
force display an interstitial page in the process that attempts to
load the index page every 10s until it succeeds.

This is only attached in production settings so the development
environment can proceed even if the migrations haven't been applied yet

awx/main/middleware.py

@@ -9,11 +9,13 @@ import six
 from django.conf import settings
 from django.contrib.auth.models import User
 from django.db.models.signals import post_save
-from django.db import IntegrityError
+from django.db.migrations.executor import MigrationExecutor
+from django.db import IntegrityError, connection
 from django.utils.functional import curry
-from django.shortcuts import get_object_or_404
+from django.shortcuts import get_object_or_404, redirect
 from django.apps import apps
 from django.utils.translation import ugettext_lazy as _
+from django.core.urlresolvers import reverse
 
 from awx.main.models import ActivityStream
 from awx.api.authentication import TokenAuthentication
@@ -162,3 +164,12 @@ class URLModificationMiddleware(object):
         if request.path_info != new_path:
             request.path = request.path.replace(request.path_info, new_path)
             request.path_info = new_path
+
+
+class MigrationRanCheckMiddleware(object):
+
+    def process_request(self, request):
+        executor = MigrationExecutor(connection)
+        plan = executor.migration_plan(executor.loader.graph.leaf_nodes())
+        if bool(plan) and 'migrations_notran' not in request.path:
+            return redirect(reverse("ui:migrations_notran"))