pkg/51465: "pkgin: empty non-autoremovable package list" error message unhelpful

[he%NetBSD.org@localhost]

>Number:         51465
>Category:       pkg
>Synopsis:       "pkgin: empty non-autoremovable package list" error message unhelpful
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Sep 09 11:50:00 +0000 2016
>Originator:     he%NetBSD.org@localhost
>Release:        NetBSD 6.1
>Organization:
	None
>Environment:
System: NetBSD stats3..... 6.1_STABLE NetBSD 6.1_STABLE (SD_VMT_TWEAK) #0: Mon Aug 22 17:31:39 CEST 2016  root@stats......:/b/obj/sys/arch/i386/compile/SD_VMT_TWEAK i386
Architecture: i386
Machine: i386
>Description:

	I'm using "pkgin" and binary packages for upgrade.

	It appears that in certain situations when doing "pkgin
	full-upgrade", pkgin can end up emitting this error message:

	pkgin: empty non-autoremovable package list

	For a naive system administrator this message may appear quite
	meaningless, and it gives no hint as to what might be the
	actual root cause of this problem -- whether it's a particular
	package which is installed (which one?) which causes the
	problem or ...

	As it turns out, this problem appears to be fixable with
	either "pkg_admin rebuild" and/or "pkg_admin rebuild-tree",
	ref.:

stats3# pkgin up
processing remote summary (http://cdn.netbsd.org/pub/pkgsrc/packages/NetBSD/i386/6.1/All)...
pkg_summary.bz2                     100% 2006KB 200.6KB/s  22.1KB/s   00:10    
stats3# pkgin fug
pkgin: empty non-autoremovable package list
stats3# pkg_admin rebuild

Stored 37911 files and 9 explicit directories from 227 packages in /var/db/pkg/pkgdb.byfile.db.
Done.
stats3# pkg_admin rebuild-tree
Done.
stats3# pkgin fug
reading local summary...
processing local summary...
calculating dependencies... done.

6 packages to be upgraded:

php56-gd-5.6.24 php56-bcmath-5.6.24 ap24-php56-5.6.24 python27-2.7.11nb2 php-5.6.24 apache-2.4.23

6 packages to be installed (31M to download, 577K to install):

python27-2.7.12 php-5.6.25 apache-2.4.23nb2 php56-gd-5.6.25 php56-bcmath-5.6.25 ap24-php56-5.6.25

proceed ? [Y/n] y
downloading packages...
...

	However, there is nothing in the error message which suggests
	this might be the problem.  The error message is therefore
	... unhelpful and should most probably be improved.

>How-To-Repeat:
	See above.

	I'm not entirely certain what brought me into this situation;
	it's conceivable it's a consequence of an earlier "pkgin fug".

>Fix:
	Improve error message, hint at dependency database rebuild?