Add autopkgtest.

debian/changelog

 python-oslo.metrics (0.4.0-2) unstable; urgency=medium
 
   * Uploading to unstable.
+  * Add autopkgtest.
 
  -- Thomas Goirand <zigo@debian.org>  Thu, 24 Mar 2022 16:24:41 +0100
 

debian/tests/control

+Tests: unittests
+Depends:
+ @,
+ @builddeps@,
+Restrictions: allow-stderr needs-root

debian/tests/unittests

+#!/bin/sh
+
+set -e
+
+pkgos-dh_auto_test --no-py2 'oslo_metrics\.tests.*'