stop playing whacamole with django and load swh-web conf to build doc

docs/conf.py

+
+import django
+import os
+os.environ.setdefault("DJANGO_SETTINGS_MODULE", "swh.web.settings.development")
+django.setup()
+
 from swh.docs.sphinx.conf import *  # NoQA

swh/docs/sphinx/conf.py

@@ -90,36 +90,4 @@ autodoc_member_order = 'bysource'
 
 # Do not import django as it needs to load its configuration file (ref: T763)
 autodoc_mock_imports = [
-    'django',
-    'django.apps',
-    'django.conf.urls',
-    'django.contrib.staticfiles.urls',
-    'django.core',
-    'django.core.cache',
-    'django.core.exceptions',
-    'django.core.paginator',
-    'django.core.wsgi',
-    'django.db',
-    'django.db.models',
-    'django.db.models.fields',
-    'django.http',
-    'django.http.multipartparser',
-    'django.http.response',
-    'django.shortcuts',
-    'django.template',
-    'django.template.response',
-    'django.test',
-    'django.test.client',
-    'django.test.signals',
-    'django.utils.encoding',
-    'django.utils.functional',
-    'django.utils.safestring',
-    'django.utils.six',
-    'django.utils.six.moves',
-    'django.utils.six.moves.http_client',
-    'django.utils.translation',
-    'django.views',
-    'django.views.decorators',
-    'django.views.decorators.csrf',
-    'django.views.generic',
 ]