feature request: more info on verbose, eg: pickling times

[qrdlgit]

I'm trying to track down why the cpus aren't getting saturated. I made verbose=55, but it doesn't show much. Is there a way to get more profile info like pickling times by joblib for input/output when verbose is large enough?

also I am getting this warning:

process_executor.py:700: UserWarning: A worker stopped while some jobs were given to the executor. This can be caused by a too short worker timeout or by a memory leak.
warnings.warn(

It'd be great if verbose was high enough to give more info about what's causing that.