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@hotmail.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.