snap-tool: exit non-zero if problem occurred

debian/changelog

@@ -1,3 +1,11 @@
+livecd-rootfs (2.568) UNRELEASED; urgency=medium
+
+  [ Tobias Koch ]
+  * Make sure snap-tool exits with non-zero exit status, if a problem
+    occurred.
+
+ -- Tobias Koch <tobias.koch@canonical.com>  Wed, 27 Feb 2019 10:16:46 +0100
+
 livecd-rootfs (2.567) disco; urgency=medium
 
   * Fix change to ignore ubiquity packages, it failed to mark anything

snap-tool

@@ -392,7 +392,8 @@ class SnapCli:
 
 if __name__ == "__main__":
     try:
-        SnapCli()(sys.argv[1:])
+        rval = SnapCli()(sys.argv[1:])
     except KeyboardInterrupt:
         sys.stderr.write("snap-tool: caught keyboard interrupt, exiting.\n")
         sys.exit(EXIT_ERR)
+    sys.exit(rval)