py_appengine_test doesn't allow python_version

[cupajoe24]

In Bazel 0.27 the default Python runtime behavior changed and as a side effect of that it seems that tests are trying to execute in Python 3 unless you explicitly specify Python 2. However py_appengine_test doesn't allow for the python_version flag. Is there any plans to add this functionality to the appengine rules or a workaround that I'm missing?