The following commit fixed the removed Django render_to_response command:
b7d36e6
It's included in git tag 3.5.2, but this change is not present in the 3.5.2 dataone.gmn package published on pypi.
I'm working around this for now by installing the pip package via git using git+https://github.com/DataONEorg/d1_python.git@3.5.2#subdirectory=gmn/src, but if it's easy to push an updated pypi package that would probably make sense.