Given the haphazard nature of Requests version permutations, this PR ignores Requests deprecation messages in error handling for now if they are the sole output on STDERR.

This is done:

• to avoid unnecessary breakage in automated CI/CD pipelines
• to simplify testing within the WP-CLI project

This should only be seen as a temporary fix until we have a better solution for dealing with Requests as a dependency shared between WP Core and WP-CLI.