port-amd64/49292: Unexpected failure installing src sets from media

[dross%pobox.com@localhost]

>Number:         49292
>Category:       port-amd64
>Synopsis:       Unexpected failure installing src sets from media
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    port-amd64-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Oct 18 18:30:00 +0000 2014
>Originator:     David Ross
>Release:        6.1.5
>Organization:
n/a
>Environment:
n/a
>Description:
Installing NetBSD, if you pick some source sets to install, the installation will fail if you proceed normally.  It's necessary to install via HTTP or some other mechanism.

I think it's fine if the src sets don't fit or shouldn't be a part of the install media.  It's just a bad experience going through install.  If the solution isn't simply to add the src sets to the media, then at least the install should guide the user to avoid this failure mode in a common install scenario.
>How-To-Repeat:
1.  Install NetBSD (amd64).
2.  As you go through the install, choose to install some src sets.
3.  Pick the option to install from "CD-ROM / DVD / install image media."
4.  Observe the error, eg: "Release set /source/sets/syssrc.tgz does not exist."
Expected behavior: A better install experience, perhaps guiding me to install via HTTP if src sets have been selected.
>Fix: