tox: Enable SQLAlchemy 2.0 warnings

As described in [1]. Unfortunately it doesn't seem to be possible to
silence these for other modules (cough...oslo.db...cough), presumably
due to how SQLAlchemy has configured warnings. We'll have to ignore
these for now.

[1] https://docs.sqlalchemy.org/en/14/changelog/migration_20.html

Change-Id: I28bc91d515440553828976dd1d3a3aef36a6d6a9
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

placement/tests/functional/fixtures/capture.py

@@ -91,11 +91,16 @@ class WarningsFixture(fixtures.Fixture):
             message='Evaluating non-mapped column expression',
             category=sqla_exc.SAWarning)
 
+        # Configure SQLAlchemy 2.0 warnings
         # TODO(stephenfin): Remove once we're using sqlalchemy 2.0 which should
-        # remove this functionality entirely
+        # remove these deprecated features entirely
+        warnings.filterwarnings(
+            'ignore',
+            category=sqla_exc.SADeprecationWarning)
+
         warnings.filterwarnings(
             'error',
-            message='Implicit coercion of SELECT and textual SELECT .*',
+            module='placement',
             category=sqla_exc.SADeprecationWarning)
 
         self.addCleanup(self._reset_warning_filters)

tox.ini

@@ -23,6 +23,8 @@ setenv =
   OS_STDERR_CAPTURE=1
   OS_TEST_TIMEOUT=160
   PYTHONDONTWRITEBYTECODE=1
+# TODO(stephenfin): Remove once we bump our upper-constraint to SQLAlchemy 2.0
+  SQLALCHEMY_WARN_20=1
 deps = -r{toxinidir}/test-requirements.txt
 # For a venv that doesn't use stestr commands must be overridden.
 commands =