Switch to pytest for unit tests

cms/conftest.py

@@ -0,0 +1,44 @@
+"""
+Studio unit test configuration and fixtures.
+
+This module needs to exist because the pytest.ini in the cms package stops
+pytest from looking for the conftest.py module in the parent directory when
+only running cms tests.
+"""
+
+from __future__ import absolute_import, unicode_literals
+
+import importlib
+import os
+import contracts
+import pytest
+
+
+def pytest_configure(config):
+    """
+    Do core setup operations from manage.py before collecting tests.
+    """
+    if config.getoption('help'):
+        return
+    enable_contracts = os.environ.get('ENABLE_CONTRACTS', False)
+    if not enable_contracts:
+        contracts.disable_all()
+    settings_module = os.environ.get('DJANGO_SETTINGS_MODULE')
+    startup_module = 'cms.startup' if settings_module.startswith('cms') else 'lms.startup'
+    startup = importlib.import_module(startup_module)
+    startup.run()
+
+
+@pytest.fixture(autouse=True, scope='function')
+def _django_clear_site_cache():
+    """
+    pytest-django uses this fixture to automatically clear the Site object
+    cache by replacing it with a new dictionary.  edx-django-sites-extensions
+    grabs the cache dictionary at startup, and uses that one for all lookups
+    from then on.  Our CacheIsolationMixin class tries to clear the cache by
+    grabbing the current dictionary from the site models module and clearing
+    it.  Long story short: if you use this all together, neither cache
+    clearing mechanism actually works.  So override this fixture to not mess
+    with what has been working for us so far.
+    """
+    pass