The document you referenced does, indeed, show how to silence it:
Making unverified HTTPS requests is strongly discouraged, however, if you understand the risks and wish to disable these warnings, you can use
disable_warnings():>>> import urllib3 >>> urllib3.disable_warnings()
You would have to edit the elasticsearch python module itself to do this. I do not think that the environment variable of PYTHONGWARNINGS=ignore or the -W flag will do anything with Curator as installed as it is typically installed, since that flag appears to be related to the launching with python script_name.py (the interpreter), and Curator runs as an endpoint, which would obviate that.
Technically, the warning is correct. If you do not allow urllib3 to validate the certificate, it is an insecure (unverified) connection, and as an admin, I prefer upstream libraries I use (like urllib3) to inform me of such things. Silencing such errors is a bit like cutting the wire under the dash of a car that lights a warning light. Preventing the light from illuminating doesn't actually mean there's no warning condition.