create_conda_env sometimes creates environment with incorrect python version

[j-wags]

For example, here, PYTHON_VER was set to be 3.6, but the resulting environment had python 3.7.

I don't understand the internals of create_conda_env.py too well, but if this behavior is inevitable, we could add a fatal check afterwards to ensure that Python is the version we requested. Alternatively, we could add a disclaimer to the create_conda_env.py docs that you're not guaranteed the python version you requested.