make sudo stop sending mail?

[Tom Horsley]

In fedora 22, sudo apparently defaults to sending mail out
about unsuccessful sudo attempts. I have a bunch of automated
tests that run on my system, one of them attempts to use sudo
to verify that it fails :-). As a result I keep getting all
sorts of mail about these failures.

I see lots of mail settings in the sudo config info, but
none of them that are described clearly enough that I can
say "Yea, that's how I turn of this annoying mail."

Is there a simple way to make the mail stop? Perhaps my
best bet it is tell it to use /bin/true as a mailer?