[BUG] rmm cannot be imported python -Werror

[hoxbro]

Describe the bug
I can't import rmm when a warning is set to always. This is a problem because I run pytest with filterwarning="always", likely I can set a ignore for the warning. But I would at least raise it here.

Steps/Code to reproduce bug
Run the following python -Werror -c "import rmm"

Expected behavior
A clear and concise description of what you expected to happen.

Environment details (please complete the following information):

• Environment location:Bare-metal
• Method of RMM install: conda
• Please run and attach the output of the rmm/print_env.sh script to gather relevant environment details

Additional context
Add any other context about the problem here.

[vyasr]

We're tracking this issue in rapidsai/build-planning#117, we'll need to make a fix that works for both newer and older versions of cuda-python.