Get test suite to full pass with SQLAlchemy 2.0

Remaining issues encountered when running with SQLAlchemy 2.0 for real:

* Never call str() on a URL and expect it to be meaningful anymore.
  The password is aggressively obfuscated now (users absolultely
  wouldn't let us leave it as is)
* More utilities and fixtures that were calling begin() within a
  block that would have already begun
* isnot is now called is_not; mocking "isnot" leads into too many
  weird compat layers
* ORM InstrumentedAttribute and internals use __slots__ now, mock
  seems to not be able to patch methods.  Ideally these tests would use
  a comparator subclass or something
* Connection.connection.connection is now called driver_connection,
  SQLAlchemy keeps the old name available however oslo.db test suite
  does not appear to tolerate the deprecation warning emitted,
  so add a compat layer
* mapper() is fully removed from 2.0, not sure if there is another
  not-yet-committed gerrit that removes mapper()

[1] https://docs.sqlalchemy.org/en/20/core/engines.html#sqlalchemy.create_engine.params.pool_pre_ping
[2] https://docs.sqlalchemy.org/en/20/changelog/changelog_20.html#change-2fe37eaf2295cebd3bb4ee8e5b8c575c
[3] https://github.com/sqlalchemy/sqlalchemy/issues/5648

Change-Id: Ifaca67c07f008d8bc0febeecd3e200cc7ee7a4b0

1 files changed, 36 insertions, 0 deletions

diff --git a/oslo_db/sqlalchemy/compat/__init__.py b/oslo_db/sqlalchemy/compat/__init__.py
new file mode 100644
index 0000000..6713696
--- /dev/null
+++ b/oslo_db/sqlalchemy/compat/__init__.py
@@ -0,0 +1,36 @@
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+from oslo_utils import versionutils
+
+from sqlalchemy import __version__
+
+
+_vers = versionutils.convert_version_to_tuple(__version__)
+sqla_2 = _vers >= (2, )
+
+
+def dialect_from_exception_context(ctx):
+    if sqla_2:
+        # SQLAlchemy 2.0 still has context.engine, however if the
+        # exception context is called in the context of a ping handler,
+        # engine is not present.  need to use dialect instead
+        return ctx.dialect
+    else:
+        return ctx.engine.dialect
+
+
+def driver_connection(connection):
+    if sqla_2:
+        return connection.connection.driver_connection
+    else:
+        return connection.connection.connection