Updated debian changelog for version 0.0.50

debian/changelog

+swh-model (0.0.50-1~swh1) unstable-swh; urgency=medium
+
+  * New upstream release 0.0.50     - (tagged by David Douard
+    <david.douard@sdfa3.org> on 2019-10-30 09:30:17 +0100)
+  * Upstream changes:     - v0.0.50
+
+ -- Software Heritage autobuilder (on jenkins-debian1) <jenkins@jenkins-debian1.internal.softwareheritage.org>  Wed, 30 Oct 2019 08:32:50 +0000
+
 swh-model (0.0.49-1~swh2) unstable-swh; urgency=medium
 
   * Add missing dependency on dulwich for tests