Add SharedModuleStoreTestCase.setUpClassAndTestData() context manager

for use when a test class has a setUpTestData() method which uses
variables set up in the setUpClass() method.
Change base teams API test class to use the context manager.

common/lib/xmodule/xmodule/modulestore/tests/django_utils.py

@@ -4,6 +4,7 @@ Modulestore configuration for test cases.
 """
 import functools
 from uuid import uuid4
+from contextlib import contextmanager
 
 from mock import patch
 
@@ -267,9 +268,10 @@ class SharedModuleStoreTestCase(TestCase):
     MODULESTORE = mixed_store_config(mkdtemp_clean(), {}, include_xml=False)
 
     @classmethod
-    def setUpClass(cls):
-        super(SharedModuleStoreTestCase, cls).setUpClass()
-
+    def _setUpModuleStore(cls):  # pylint: disable=invalid-name
+        """
+        Set up the modulestore for an entire test class.
+        """
         cls._settings_override = override_settings(MODULESTORE=cls.MODULESTORE)
         cls._settings_override.__enter__()
         XMODULE_FACTORY_LOCK.enable()
@@ -277,6 +279,40 @@ class SharedModuleStoreTestCase(TestCase):
         cls.store = modulestore()
 
     @classmethod
+    @contextmanager
+    def setUpClassAndTestData(cls):  # pylint: disable=invalid-name
+        """
+        For use when the test class has a setUpTestData() method that uses variables
+        that are setup during setUpClass() of the same test class.
+
+        Use it like so:
+
+        @classmethod
+        def setUpClass(cls):
+            with super(MyTestClass, cls).setUpClassAndTestData():
+                <all the cls.setUpClass() setup code that performs modulestore setup...>
+
+        @classmethod
+        def setUpTestData(cls):
+            <all the setup code that creates Django models per test class...>
+            <these models can use variables (courses) setup in setUpClass() above>
+        """
+        cls._setUpModuleStore()
+        # Now yield to allow the test class to run its setUpClass() setup code.
+        yield
+        # Now call the base class, which calls back into the test class's setUpTestData().
+        super(SharedModuleStoreTestCase, cls).setUpClass()
+
+    @classmethod
+    def setUpClass(cls):
+        """
+        For use when the test class has no setUpTestData() method -or-
+        when that method does not use variable set up in setUpClass().
+        """
+        super(SharedModuleStoreTestCase, cls).setUpClass()
+        cls._setUpModuleStore()
+
+    @classmethod
     def tearDownClass(cls):
         drop_mongo_collections()  # pylint: disable=no-value-for-parameter
         clear_all_caches()