add mypy coverage task

get mypy plugin to be able to have coverage

Change-Id: I8c2d57bb97bd522b83d20a0f97576c7ae9ea71a5

Author: zzzeek

tox.ini

@@ -148,9 +148,22 @@ deps=
      importlib_metadata; python_version < '3.8'
      mypy
      patch==1.*
+
 commands =
     pytest -m mypy {posargs}
 
+[testenv:mypy-cov]
+
+deps=
+     {[testenv:mypy]deps}
+     pytest-cov
+
+commands =
+    pytest -m mypy {env:COVERAGE} {posargs}
+
+setenv=
+    COVERAGE={[testenv]cov_args}
+
 # thanks to https://julien.danjou.info/the-best-flake8-extensions/
 [testenv:lint]
 basepython = python3