bug#28393: Sound output broken in Audacity

[Mark H Weaver]

Sound output is broken in Audacity on my Thinkpad X200 running GuixSD,
at least within GNOME 3 (I haven't tried it anywhere else).  It worked
in the past.  I see the following error messages in Audacity's
stdout/stderr:

(audacity:893): Gtk-WARNING **: Unable to locate theme engine in module_path: 
"adwaita",

(audacity:893): Gtk-WARNING **: Unable to locate theme engine in module_path: 
"adwaita",
ALSA lib pcm.c:2501:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear
ALSA lib pcm.c:2501:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe
ALSA lib pcm.c:2501:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side
ALSA lib pcm_route.c:867:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:867:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:867:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:867:(find_matching_chmap) Found no matching channel map
Expression 'stream->playback.pcm' failed in 'src/hostapi/alsa/pa_linux_alsa.c', 
line: 4628
Expression 'stream->playback.pcm' failed in 'src/hostapi/alsa/pa_linux_alsa.c', 
line: 4628
Expression 'stream->playback.pcm' failed in 'src/hostapi/alsa/pa_linux_alsa.c', 
line: 4628

       Mark