BUG #13958: Missing docs on error

The following bug has been logged on the website:

Bug reference: 13958
Logged by: Brian G
Email address: public88878878887(at)hotmail(dot)com
PostgreSQL version: 9.4.6
Operating system: Ubuntu 14
Description:

The dreaded "FATAL: Peer authentication failed ..." error needs information
on how to use your product. Every time I try to use PSQL I have to fight
this battle again. There are a hundred thousand pages about it on the web,
but 99% of most fixes don't work. Is there a definitive guide you could
post so folks could get their development environment running? Why is this
such a big problem? I've wasted a bunch of hours --again-- and this still
doesn't work. To me, pq is a product that should "not be used solely
because of this". I won't allow it at our organization except under
exceptional circumstances, because of this error. I would love to see a
Postgres-branded guide to fixing this (not explaining how OS authorisation
works in full, just fixing the error) that makes your product more usable.