grml2usb: print backtrace when --verbose is given

Useful for debugging.

diff --git a/grml2usb b/grml2usb
index f15dbf6..9c6c8c5 100755 (executable)
--- a/grml2usb
+++ b/grml2usb
@@ -1932,6 +1932,8 @@ def main():
 
     except Exception as error:
         logging.critical("Fatal: %s", str(error))
+        if options.verbose:
+            logging.exception("Exception:")
         sys.exit(1)