Add release note for base test class removal

In change I1e71150ba6daeba464b6ed8d46163f1f34959db3 we removed the
legacy base test classes, first deprecated in 2015. We forgot to include
a release note, however. Address this now.

Change-Id: I4d66f0308b89a187143ef6c8495383fe60043c14
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

oslo_db/sqlalchemy/enginefacade.py

@@ -553,7 +553,7 @@ class _TestTransactionFactory(_TransactionFactory):
     Note that while this is used by oslo.db's own tests of
     the enginefacade system, it is also exported for use by
     the test suites of other projects, first as an element of the
-    oslo_db.sqlalchemy.test_base module, and secondly may be used by
+    oslo_db.sqlalchemy.test_fixtures module, and secondly may be used by
     external test suites directly.
 
     Includes a feature to inject itself temporarily as the factory

oslo_db/sqlalchemy/test_fixtures.py

@@ -546,9 +546,9 @@ def optimize_package_test_loader(file_):
 
     The function is invoked as::
 
-        from oslo_db.sqlalchemy import test_base
+        from oslo_db.sqlalchemy import test_fixtures
 
-        load_tests = test_base.optimize_package_test_loader(__file__)
+        load_tests = test_fixtures.optimize_package_test_loader(__file__)
 
     The loader *must* be present in the package level __init__.py.
 
@@ -586,9 +586,9 @@ def optimize_module_test_loader():
 
     The function is invoked as::
 
-        from oslo_db.sqlalchemy import test_base
+        from oslo_db.sqlalchemy import test_fixtures
 
-        load_tests = test_base.optimize_module_test_loader()
+        load_tests = test_fixtures.optimize_module_test_loader()
 
     The loader *must* be present in an individual module, and *not* the
     package level __init__.py.

releasenotes/notes/remove-base-test-classes-557889ec4f072781.yaml

@@ -0,0 +1,24 @@
+---
+upgrade:
+  - |
+    The following test fixtures and base test classes were deprecated and have
+    now been removed:
+
+    - ``oslo_db.sqlalchemy.test_base.DbFixture``
+    - ``oslo_db.sqlalchemy.test_base.DbTestCase``
+    - ``oslo_db.sqlalchemy.test_base.OpportunisticTestCase``
+    - ``oslo_db.sqlalchemy.test_base.MySQLOpportunisticFixture``
+    - ``oslo_db.sqlalchemy.test_base.PostgreSQLOpportunisticFixture``
+    - ``oslo_db.sqlalchemy.test_base.MySQLOpportunisticTestCase``
+    - ``oslo_db.sqlalchemy.test_base.PostgreSQLOpportunisticTestCase``
+
+    They have all been replaced by equivalent test fixtures and test class
+    mixins in ``oslo_db.sqlalchemy.test_fixtures``.
+
+    In addition, the following test cases were being inadvertently used
+    publicly despite being private to oslo.db. They were also deprecated and
+    have now been removed:
+
+    - ``oslo_db.tests.sqlalchemy.base.DbTestCase``
+    - ``oslo_db.tests.sqlalchemy.base.MySQLOpportunisticTestCase``
+    - ``oslo_db.tests.sqlalchemy.base.PostgreSQLOpportunisticTestCase``