BUG #14009: pg_restore not restoring privilegs when one login/group role is missing

The following bug has been logged on the website:

Bug reference:      14009
Logged by:          Alexander Spiteri
Email address:      alexander@spiteri.org
PostgreSQL version: 9.5.1
Operating system:   CentOS Linux release 7.2.1511 (Core)
Description:

I have just installed a new instance of postgres 9.5.1 and have an issue
with restoring the database, specifically privilges of the login/group
roles.

In the past I was working with postgres 8.4 and when I took a backup from
the live server to the testing server pg_restore would grant all privilages
to login/group roles which existed on the testing server and give an error
for those that do not exist.

On the new 9.5.1 server when I try to restore a database, if one login/group
role does not exist pg_restore gives an error about it and then does not
grant any rights to all the other login/group roles that do exist. No errors
/ notices are issued about the grants that are not applied.

This behaviour is puzzling. I expected to get errors for users that are not
found but why aren't privilges assigned to users that do exist?

I reproduced this behaviour on different installations running version 9.5.1
and 9.3.11.