Hi, please find attached a debdiff that fixes the crash.
Cheers - Bruno
diff -Nru soundconverter-3.0.1/debian/changelog soundconverter-3.0.1/debian/changelog
--- soundconverter-3.0.1/debian/changelog 2019-02-01 09:28:03.000000000 +0100
+++ soundconverter-3.0.1/debian/changelog 2019-02-07 18:55:19.000000000 +0100
@@ -1,3 +1,12 @@
+soundconverter (3.0.1-2) UNRELEASED; urgency=medium
+
+ * Fix Doesn't start. (Closes: #FIXME)
+ + Add dont-fail-on-missing-gconf.patch to ignore a ValueError exception
+ possibly thrown by gi.require_version('GConf', '2.0') when gconf is not
+ installed.
+
+ -- Bruno Kleinert <fu...@debian.org> Thu, 07 Feb 2019 18:55:19 +0100
+
soundconverter (3.0.1-1) unstable; urgency=medium
[ Felipe Sateler ]
diff -Nru soundconverter-3.0.1/debian/patches/dont-fail-on-missing-gconf.patch soundconverter-3.0.1/debian/patches/dont-fail-on-missing-gconf.patch
--- soundconverter-3.0.1/debian/patches/dont-fail-on-missing-gconf.patch 1970-01-01 01:00:00.000000000 +0100
+++ soundconverter-3.0.1/debian/patches/dont-fail-on-missing-gconf.patch 2019-02-07 18:46:44.000000000 +0100
@@ -0,0 +1,13 @@
+Index: soundconverter/soundconverter/gstreamer.py
+===================================================================
+--- soundconverter.orig/soundconverter/gstreamer.py 2019-02-07 18:44:26.218796531 +0100
++++ soundconverter/soundconverter/gstreamer.py 2019-02-07 18:46:41.964610487 +0100
+@@ -90,6 +90,8 @@
+ audio_profiles_dict[description] = profile
+ except ImportError:
+ pass
++except ValueError:
++ pass
+
+ required_elements = ('decodebin', 'fakesink', 'audioconvert', 'typefind', 'audiorate')
+ for element in required_elements:
diff -Nru soundconverter-3.0.1/debian/patches/series soundconverter-3.0.1/debian/patches/series
--- soundconverter-3.0.1/debian/patches/series 1970-01-01 01:00:00.000000000 +0100
+++ soundconverter-3.0.1/debian/patches/series 2019-02-07 18:44:17.000000000 +0100
@@ -0,0 +1 @@
+dont-fail-on-missing-gconf.patch
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