add module import test to fix pyflakes issue

Author: fdiblen

{{cookiecutter.project_name}}/tests/test_my_module.py

@@ -6,6 +6,10 @@
 from {{ cookiecutter.package_name }} import my_module
 
 
+def test_module_import():
+    assert my_module not in sys.modules
+
+
 def test_something():
     assert True