BUG #11090: Unclear error message in pg_upgrade

The following bug has been logged on the website:

Bug reference: 11090
Logged by: Bror Jonsson
Email address: brorfred(at)gmail(dot)com
PostgreSQL version: 9.2.0
Operating system: Mac OS X
Description:

pg_upgrade requires that the old and new database has the same install
superuser (superuser that ran initdb). If this requirement isn't fulfilled,
you'll get the following error:

"Old and new cluster install users have different values for
pg_authid.oid.\n"

(https://github.com/postgres/postgres/blob/master/contrib/pg_upgrade/check.c,
line 168)

This was very confusing to me. A suggested rephrase would be:

"Old and new cluster must be created by the same user. Try to re-init the
new database with the flag "-U %s" \n"

Where %s is the the install user in the old cluster.