TOX updated to only test baangt unit test

tox.ini

@@ -1,7 +1,7 @@
 # content of: tox.ini , put in same dir as setup.py
 [tox]
-envlist = py36, py37, py38
-tox_pyenv_fallback=False
+envlist = py37
+# tox_pyenv_fallback=False
 
 [testenv]
 # install pytest in the virtualenv where commands will be executed
@@ -11,4 +11,4 @@ deps =
 commands =
     # NOTE: you can run any command line tool here - not just tests
     python -V
-    pytest
+    pytest tests