Add ament_mypy to quality_of_service_demo_py

quality_of_service_demo/rclpy/package.xml

@@ -23,6 +23,7 @@
   <test_depend>ament_pep257</test_depend>
   <test_depend>ament_xmllint</test_depend>
   <test_depend>python3-pytest</test_depend>
+  <test_depend>ament_mypy</test_depend>
 
   <export>
     <build_type>ament_python</build_type>

quality_of_service_demo/rclpy/test/test_mypy.py

@@ -0,0 +1,21 @@
+# Copyright 2019 Canonical, Ltd.
+#
+# 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.
+
+
+from ament_mypy.main import main
+
+
+def test_mypy() -> None:
+    rc = main(argv=['--ament-strict'])
+    assert rc == 0, 'Found code style errors / warnings'