justin: exit with failure if regexp does not match

This change will avoid an ugly stacktrace, but the issue is still present. The
"real" error message won't be drowned out though.

lib/svtplay_dl/service/justin.py

@@ -38,6 +38,7 @@ class Justin(Service):
                 match = re.search(r"embedSWF\(\"(.*)\", \"live", data)
                 if not match:
                     log.error("Can't find swf file.")
+                    sys.exit(2)
                 options.other = check_redirect(match.group(1))
                 url = "http://usher.justin.tv/find/%s.xml?type=any&p=2321" % user
                 options.live = True