Problem: pulp-manager is not needed

Solution: use django-admin directly

re: #4450
https://pulp.plan.io/issues/4450

.travis/script.sh

@@ -8,15 +8,15 @@ flake8 --config flake8.cfg || exit 1
 # Run migrations.
 export DJANGO_SETTINGS_MODULE=pulpcore.app.settings
 export PULP_CONTENT_HOST=localhost:8080
-pulp-manager makemigrations docker
-pulp-manager migrate --noinput
+django-admin makemigrations docker
+django-admin migrate --noinput
 
 # Run unit tests.
 (cd ../pulpcore && coverage run manage.py test pulp_docker.tests.unit)
 
 # Run functional tests.
-pulp-manager reset-admin-password --password admin
-pulp-manager runserver >> ~/django_runserver.log 2>&1 &
+django-admin reset-admin-password --password admin
+django-admin runserver >> ~/django_runserver.log 2>&1 &
 gunicorn pulpcore.content:server --bind 'localhost:8080' --worker-class 'aiohttp.GunicornWebWorker' -w 2 >> ~/content_app.log 2>&1 &
 rq worker -n 'resource-manager@%h' -w 'pulpcore.tasking.worker.PulpWorker' >> ~/resource_manager.log 2>&1 &
 rq worker -n 'reserved-resource-worker-1@%h' -w 'pulpcore.tasking.worker.PulpWorker' >> ~/reserved_worker-1.log 2>&1 &

README.rst

@@ -74,15 +74,15 @@ Make and Run Migrations
 
 .. code-block:: bash
 
-   pulp-manager makemigrations docker
-   pulp-manager migrate docker
+   django-admin makemigrations docker
+   django-admin migrate docker
 
 Run Services
 ------------
 
 .. code-block:: bash
 
-   pulp-manager runserver
+   django-admin runserver
    gunicorn pulpcore.content:server --bind 'localhost:8080' --worker-class 'aiohttp.GunicornWebWorker' -w 2
    sudo systemctl restart pulp-resource-manager
    sudo systemctl restart pulp-worker@1