[exceptions] Save caught exception as base_exc attribute.

[rbdixon]

Reports may wish to make a decision based on the nature of the
underlying exception. In addition to the traceback the CatchedException
also retains the underlying exception as the base_exc attribute.

This is useful for custom tooling that is based on doit. If the task has already displayed a comprehensive error message to the user the Python stack trace is confusing. My custom reporter looks at the base exception and will suppress the stack trace as needed.

[coveralls]

Coverage increased (+3.0e-05%) to 99.743% when pulling ca7dce0 on rbdixon:save_exception into 85c995c on pydoit:master.

[rbdixon]

The build failures look to be something unrelated to this one-line change.

[schettino72]

In addition to the traceback the CatchedException also retains the underlying exception as the base_exc attribute.

I think this might be a problem. As far as I remember CatchedException is pickled and passed when using a parallel multi-process runner. So if the original Exception contains and object that can not be pickled this would break the runner...

Could you please try running some sample with multi-process?
I did not double-check this is really a problem and I could be wrong.
Note that if a base exception is pickleable you would not be able to guarantee that every Exception is pickleable.

This is useful for custom tooling that is based on doit. If the task has already displayed a comprehensive error message to the user the Python stack trace is confusing. My custom reporter looks at the base exception and will suppress the stack trace as needed.

A task might also return a plain False value to indicate that it has failed.
So (maybe) another option for your use-case would be just for you to wrap this logic in the task's action itself without relying on changes in the reporter.

So I am not sure about accepting this PR...
I would be ok on adding more attributes to CachedException as long as they are pickleable.

[rbdixon]

ok, thanks. I have not tracked the multi-process work so I was not aware of this.