Add support for the no_proxy environment variable.

Review Request #667 — Created May 24, 2021 and submitted — Latest diff uploaded

Information

pidgin/pidgin
release-2.x.y
e5ac6a37a937

Reviewers

This started as a patch on https://issues.imfreedom.org/issue/PIDGIN-17518
but I cleaned it up a bit as well.

Followed the unit tests that are documented in the diff.