When performing some action on another user's repo, you will see the message
Not trusting file /home/bob/repo/.hg/hgrc from untrusted user bob, group users
This is fine, and I don't necessarily want to trust bob, but when running certain commands, I don't want to see this output as it can interfere. It is printed to stderr, but I don't want to redirect all stderr output to null, nor do I want to redirect it to stdout and suppress it.
Is there any way to simply prevent mercurial from printing this? -q does not do it.
Yes, you can configure the warning:
[ui]
report_untrusted = False
The config settings are documented online and in the built-in help (hg help config) and in the manual page (man hgrc on a Unix-like system).