Bug#991962: src: prefix should work also with experimental source only

[Patrice Duroux <patrice.duroux@gmail.com>]

Package: reportbug
Version: 7.10.3
Severity: wishlist

Dear Maintainer,

   * What led up to the situation?

$ reportbug src:gtk4

   * What exactly did you do (or not do) that was effective (or
     ineffective)?

I would like to report a «bug» that affect both libgtk-4-bin and libgtk-4-1
(4.3.1+ds-2):

$ apt-file search /usr/share/doc/@BIN_PKG@
libgtk-4-bin: /usr/share/doc/@BIN_PKG@/@NEWS@
libgtk-4-bin: /usr/share/doc/@BIN_PKG@/@README.md@
$ apt-file search /usr/share/doc/@SHARED_PKG@
libgtk-4-1: /usr/share/doc/@SHARED_PKG@/@NEWS@
libgtk-4-1: /usr/share/doc/@SHARED_PKG@/@README.md@


   * What was the outcome of this action?

W: Unable to locate package gtk4

   * What outcome did you expect instead?

The same as reportbug src:gtk+3.0 for instance.


Thanks,
Patrice


-- Package-specific info:
** Environment settings:
INTERFACE="gtk"

** /home/patrice/.reportbugrc:
email "patrice.duroux@gmail.com"
realname "Patrice Duroux"
ui gtk
smtphost smtp.orange.fr

-- System Information:
Debian Release: 11.0
  APT prefers unstable-debug
  APT policy: (500, 'unstable-debug'), (500, 'unstable'), (1, 'experimental-debug'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 5.10.0-8-amd64 (SMP w/12 CPU threads)
Locale: LANG=fr_FR.UTF-8, LC_CTYPE=fr_FR.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages reportbug depends on:
ii  apt                2.2.4
ii  python3            3.9.2-3
ii  python3-reportbug  7.10.3
ii  sensible-utils     0.0.14

reportbug recommends no packages.

Versions of packages reportbug suggests:
pn  claws-mail                                 <none>
pn  debconf-utils                              <none>
pn  debsums                                    <none>
pn  dlocate                                    <none>
pn  emacs-bin-common                           <none>
ii  exim4-daemon-light [mail-transport-agent]  4.94.2-7
ii  file                                       1:5.39-3
ii  gnupg                                      2.2.27-2
pn  python3-urwid                              <none>
pn  reportbug-gtk                              <none>
ii  xdg-utils                                  1.1.3-4.1

Versions of packages python3-reportbug depends on:
ii  apt                2.2.4
ii  file               1:5.39-3
ii  python3            3.9.2-3
ii  python3-apt        2.2.1
ii  python3-debian     0.1.39
ii  python3-debianbts  3.1.0
ii  python3-requests   2.25.1+dfsg-2
ii  sensible-utils     0.0.14

python3-reportbug suggests no packages.

-- no debconf information