csbackchk: fix return in try-except-else conditional

csbackchk.py

@@ -268,6 +268,7 @@ def main(argv=None):
     sys.stderr.write("unknown execption!")
     logger.getLogger().error(abortmessage)
     sys.stderr.write(abortmessage)
+    return 999
   else:
     logger.getLogger().info("Checks performed.")
     return 0