add collect tests tox env

Author: danabens

tox.ini

@@ -163,3 +163,15 @@ deps =
 commands =
     python setup.py sdist
     twine check dist/*.tar.gz
+
+[testenv:collect-tests]
+# this needs to succeed for tests to display in some IDEs
+extras = test
+deps =
+    boto3 >= 1.12.8
+    python-dateutil
+    pytest
+    pytest-cov
+    docker
+commands =
+    pytest --collect-only