tests: Add warning fixture

Copied almost wholesale from Nova. We're going to use this as part of
the SQLAlchemy 2.0 preparation. We enable those warnings and clean up
the tox file in preparation.

Change-Id: I869d9b110264d69301bf43ae579a4749adeba4f6
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

freezer_api/tests/unit/common.py

@@ -28,6 +28,7 @@ import testtools
 
 from freezer_api.common import config
 from freezer_api import policy
+from freezer_api.tests.unit import fixtures as freezer_fixtures
 
 CONF = cfg.CONF
 
@@ -697,6 +698,8 @@ class FreezerBaseTestCase(testtools.TestCase):
         elif self.REGISTER_POLICY:
             raise Exception('You need to register config to register policy')
 
+        self.useFixture(freezer_fixtures.WarningsFixture())
+
         self.test_dir = self.useFixture(fixtures.TempDir()).path
         self.conf_dir = os.path.join(self.test_dir, 'etc')
         os.makedirs(self.conf_dir)

freezer_api/tests/unit/fixtures.py

@@ -0,0 +1,56 @@
+# 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.
+
+import warnings
+
+import fixtures
+from sqlalchemy import exc as sqla_exc
+
+
+class WarningsFixture(fixtures.Fixture):
+    """Filters out warnings during test runs."""
+
+    def setUp(self):
+        super().setUp()
+
+        self._original_warning_filters = warnings.filters[:]
+
+        warnings.simplefilter("once", DeprecationWarning)
+
+        # Enable SQLAlchemy deprecation warnings to capture upcoming changes to
+        # that library
+
+        warnings.filterwarnings(
+            'ignore',
+            category=sqla_exc.SADeprecationWarning,
+        )
+
+        warnings.filterwarnings(
+            'error',
+            module='freezer_api',
+            category=sqla_exc.SADeprecationWarning,
+        )
+
+        # Enable general SQLAlchemy warnings also to ensure we're not doing
+        # silly stuff. It's possible that we'll need to filter things out here
+        # with future SQLAlchemy versions, but that's a good thing
+
+        warnings.filterwarnings(
+            'error',
+            module='freezer_api',
+            category=sqla_exc.SAWarning,
+        )
+
+        self.addCleanup(self._reset_warning_filters)
+
+    def _reset_warning_filters(self):
+        warnings.filters[:] = self._original_warning_filters

tox.ini

@@ -1,28 +1,58 @@
 [tox]
 minversion = 3.18.0
 envlist = py3,pep8,pylint,docs
-ignore_basepython_conflict = True
 
 [testenv]
-basepython = python3
-usedevelop = True
-allowlist_externals = rm
+usedevelop = true
+allowlist_externals =
+  rm
 deps =
-    -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
-    -r{toxinidir}/requirements.txt
-    -r{toxinidir}/test-requirements.txt
-
-passenv = HTTP_PROXY, HTTPS_PROXY, NO_PROXY, OS_DEBUG, GENERATE_HASHES
-commands = stestr run {posargs}
+  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -r{toxinidir}/requirements.txt
+  -r{toxinidir}/test-requirements.txt
+setenv =
+  PYTHONDONTWRITEBYTECODE=1
+# TODO(stephenfin): Remove once we bump our upper-constraint to SQLAlchemy 2.0
+  SQLALCHEMY_WARN_20=1
+passenv =
+  HTTP_PROXY
+  HTTPS_PROXY
+  NO_PROXY
+  OS_DEBUG
+  GENERATE_HASHES
+commands =
+  stestr run {posargs}
 
 [testenv:venv]
-commands = {posargs}
+commands =
+  {posargs}
 
 [testenv:pylint]
-commands = pylint --rcfile .pylintrc freezer_api
+commands =
+  pylint --rcfile .pylintrc freezer_api
 
 [testenv:pep8]
-commands = flake8 freezer_api
+commands =
+  flake8 freezer_api
+
+[testenv:docs]
+commands =
+  rm -rf api-ref/build
+#  sphinx-build -W --keep-going -b html api-ref/source api-ref/build/html
+  sphinx-build -W --keep-going -b html doc/source doc/build/html
+
+[testenv:api-ref]
+commands =
+  rm -rf api-ref/build
+  sphinx-build -W -a -E --keep-going -b html -d api-ref/build/doctrees api-ref/source api-ref/build/html
+
+[testenv:releasenotes]
+commands =
+  sphinx-build -W -a -E -d releasenotes/build/doctrees --keep-going -b html releasenotes/source releasenotes/build/html
+
+[testenv:genpolicy]
+commands =
+  oslopolicy-sample-generator --config-file etc/freezer/freezer-policy-generator.conf
 
 [flake8]
 # Ignored hackings:
@@ -31,21 +61,5 @@ commands = flake8 freezer_api
 # H404 -> Multi line docstrings should start without a leading new line.
 # H405 -> Multi line docstrings should start with a one line summary followed by an empty line.
 ignore = H202,H401,H404,H405
-show-source = True
+show-source = true
 exclude = .venv,.tox,dist,doc,*egg,specs,build,*/source/conf.py
-
-[testenv:docs]
-commands =
-  rm -rf api-ref/build
-#  sphinx-build -W --keep-going -b html api-ref/source api-ref/build/html
-  sphinx-build -W --keep-going -b html doc/source doc/build/html
-[testenv:api-ref]
-commands =
-  rm -rf api-ref/build
-  sphinx-build -W -a -E --keep-going -b html -d api-ref/build/doctrees api-ref/source api-ref/build/html
-
-[testenv:releasenotes]
-commands = sphinx-build -W -a -E -d releasenotes/build/doctrees --keep-going -b html releasenotes/source releasenotes/build/html
-
-[testenv:genpolicy]
-commands = oslopolicy-sample-generator --config-file etc/freezer/freezer-policy-generator.conf