Sync release-tools

Sync release-tools boilerplate containing these changes
in order to pin pip < 20.3:
https://github.com/openstack-charmers/release-tools/pull/125
https://github.com/openstack-charmers/release-tools/pull/126

Change-Id: Ie522cb20b0ea308de9783dd9b7e0750f4aba3072

test-requirements.txt

@@ -9,11 +9,42 @@
 #
 setuptools<50.0.0  # https://github.com/pypa/setuptools/commit/04e3df22df840c6bb244e9b27bc56750c44b7c85
 charm-tools>=2.4.4
+
+# Workaround until https://github.com/juju/charm-tools/pull/589 gets
+# published
+keyring<21
+
 requests>=2.18.4
-mock>=1.2
+
+# Newer mock seems to have some syntax which is newer than python3.5 (e.g.
+# f'{something}'
+mock>=1.2,<4.0.0; python_version < '3.6'
+mock>=1.2; python_version >= '3.6'
+
 flake8>=2.2.4
 stestr>=2.2.0
+
+# Dependency of stestr. Workaround for
+# https://github.com/mtreinish/stestr/issues/145
+cliff<3.0.0
+
+# Dependencies of stestr. Newer versions use keywords that didn't exist in
+# python 3.5 yet (e.g. "ModuleNotFoundError")
+importlib-metadata<3.0.0; python_version < '3.6'
+importlib-resources<3.0.0; python_version < '3.6'
+
+# Some Zuul nodes sometimes pull newer versions of these dependencies which
+# dropped support for python 3.5:
+osprofiler<2.7.0;python_version<'3.6'
+stevedore<1.31.0;python_version<'3.6'
+
 coverage>=4.5.2
 pyudev              # for ceph-* charm unit tests (need to fix the ceph-* charm unit tests/mocking)
 git+https://github.com/openstack-charmers/zaza.git#egg=zaza;python_version>='3.0'
 git+https://github.com/openstack-charmers/zaza-openstack-tests.git#egg=zaza.openstack
+
+# Needed for charm-glance:
+git+https://opendev.org/openstack/tempest.git#egg=tempest;python_version>='3.6'
+tempest<24.0.0;python_version<'3.6'
+
+croniter            # needed for charm-rabbitmq-server unit tests