Bundle a copy of github.com/nir0s/distro/distro.py

Since the 'platform.dist()' and 'platform.linux_distribution()'
methods will be removed from future versions of python, this
provides an alternative to replace ansibles use of those
methods.

lib/ansible/module_utils/distro.py is a copy of
https://github.com/nir0s/distro/blob/master/distro.py

This module is originally from https://github.com/nir0s/distro
and is license under the Apache License, Version 2.0.

test/units/module_utils/test_distro.py

@@ -0,0 +1,32 @@
+
+# (c) 2018 Adrian Likins <alikins@redhat.com>
+# Copyright (c) 2018 Ansible Project
+# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
+#  or
+# Apache License v2.0 (see http://www.apache.org/licenses/LICENSE-2.0)
+#
+# Dual licensed so any test cases could potentially be included by the upstream project
+# that module_utils/distro.py is from (https://github.com/nir0s/distro)
+
+
+# Note that nir0s/distro has many more tests in it's test suite. The tests here are
+# primarily for testing the vendoring.
+
+import pytest
+
+from ansible.module_utils import distro
+
+
+# Generic test case with minimal assertions about specific returned values.
+class TestDistro():
+    # should run on any platform without errors, even if non-linux without any
+    # useful info to return
+    def test_info(self):
+        info = distro.info()
+        assert isinstance(info, dict), \
+            'distro.info() returned %s (%s) which is not a dist' % (info, type(info))
+
+    def test_linux_distribution(self):
+        linux_dist = distro.linux_distribution()
+        assert isinstance(linux_dist, tuple), \
+            'linux_distrution() returned %s (%s) which is not a tuple' % (linux_dist, type(linux_dist))