Logging error on lmtp not created.

This I hope logs when lmtp fails to be created.

docs/courier-to-mailman3.md

@@ -28,4 +28,5 @@ This is our current version trying to communicate between courier and mailman3.
   * Format had errors with `$` used instead of `%`
 * Clean up logging to not log what was logged for logging diagnostics.
 * Logging host and port on same line.
-* OK, parsing port number, and setting default.
+* OK, parsing port number, and setting default.
+* Logging error (I hope), when lmtp fails to be created.

source/courier-to-mailman3.py

@@ -65,5 +65,6 @@ try:
         # 5xx error
         else:
             raise
-except:
+except smtplib.SMTPEXception as e:
+    logger.error('lmtp failed errorno: %s, message: %s', e.errno, e.strerror)
     exit(100)