Temp fix to apply migrations correctly to staging/prod DBs

This one is pretty obscure

There are a couple of issues with third party plugin migrations we need to solve here:

1. https://github.com/aldryn/aldryn-video/blob/126580c04fc6c0c60d23361280d56bd5333f5c51/aldryn_video/migrations/0001_initial.py#L11-L12
   depends on `__latest__`
   (which is essentially bug in most cases for this reason). Having already
   applied `aldryn_video 0001` now means we can't apply `cms 0016`
   the `temp_migration_settings` file allows us to temporarily un-register
   `aldryn_video` by running
   `python manage.py migrate cms 0016 --settings foundation.temp_migration_settings`
   without either breaking the site or failing on
   `django.db.migrations.exceptions.InconsistentMigrationHistory: Migration aldryn_video.0001_initial is applied before its dependency cms.0016_auto_20160608_1535 on database 'default'.`
2. Some other migration relies on `easy_thumbnails 0001` but doesn't declare
   it as a migration dependency, so we need to run
   `python manage.py migrate easy_thumbnails` to avoid throwing
   `django.db.utils.ProgrammingError: relation "easy_thumbnails_source" does not exist`
3. Once we've done those we can run `python manage.py migrate`
   to apply the remaining issues without error

Once we've run this once on staging and once on production to migrate
the existing DBs correctly, we can do another commit to revert this change
and delete `temp_migration_settings`
and set CMD back to
`python manage.py migrate && python manage.py update_index && /usr/bin/supervisord`
before the next deploy.

Dockerfile

@@ -36,4 +36,8 @@ EXPOSE $PORT
 
 RUN python manage.py collectstatic --noinput
 
-CMD python manage.py migrate && python manage.py update_index && /usr/bin/supervisord
+CMD python manage.py migrate cms 0016 --settings foundation.temp_migration_settings &&\
+    python manage.py migrate easy_thumbnails &&\
+    python manage.py migrate &&\
+    python manage.py update_index &&\
+    /usr/bin/supervisord

foundation/temp_migration_settings.py

@@ -0,0 +1,3 @@
+from settings import *  # flake8: noqa
+INSTALLED_APPS = list(INSTALLED_APPS)
+INSTALLED_APPS.remove('aldryn_video')  # flake8: noqa