Upgrade django from 1.8 to 1.11

[chouseknecht]

From @cutwater on October 11, 2017 11:45

Action items:

• Replace patterns() with lists of urls.
  > django.conf.urls.patterns() is deprecated and will be removed in Django 1.10.
  Fixed in Drop deprecated patterns() function usage #200

• Replace string views with callables.
  > Support for string view arguments to url() is deprecated and will be removed in Django 1.10.
  Fixed in Drop deprecated patterns() function usage #200

• Replace usage of django.utils.importlib
  Remove django-site-maintenance dependency.
  > django.utils.importlib will be removed in Django 1.9.

• Upgrade djangorestframework

More changes to be added.

Copied from original issue: ansible/galaxy-issues#294

[cutwater]

Replace usage of django.utils.importlib

Deprecation warning comes from maintanance python library. As far as we don't use it, we can safely remove it in order to upgrade to Django 1.11.

[cutwater]

Latest drt-haystack==1.6.1 doesn't support django 1.11.
We use version 1.5.6 which fails with exception:

Traceback (most recent call last):
  File "/var/lib/galaxy/venv/lib/python2.7/site-packages/django/core/handlers/exception.py", line 41, in inner
    response = get_response(request)
  File "/var/lib/galaxy/venv/lib/python2.7/site-packages/django/core/handlers/base.py", line 249, in _legacy_get_response
    response = self._get_response(request)
  File "/var/lib/galaxy/venv/lib/python2.7/site-packages/django/core/handlers/base.py", line 187, in _get_response
    response = self.process_exception_by_middleware(e, request)
...
  File "/var/lib/galaxy/venv/lib/python2.7/site-packages/rest_framework/serializers.py", line 363, in fields
    for key, value in self.get_fields().items():
  File "/var/lib/galaxy/venv/lib/python2.7/site-packages/drf_haystack/serializers.py", line 154, in get_fields
    kwargs = self._get_default_field_kwargs(model, field_type)
  File "/var/lib/galaxy/venv/lib/python2.7/site-packages/drf_haystack/serializers.py", line 79, in _get_default_field_kwargs
    if field.model_attr in model._meta.get_all_field_names():
AttributeError: 'Options' object has no attribute 'get_all_field_names'

Should be resolved after #193.

[cutwater]

Fixed by #351