1. added error_logger; 2.changed the function called when wrangler is switched on/off.
1. added error_logger; 2.changed the function called when wrangler is switched on/off.

prowessproject/wrangler,andrzejsliwa/wrangler,arcusfelis/wrangler,arcusfelis/wrangler,tdb/wrangler,bsmr-erlang/wrangler