--use-python-path is an attractive nuisance

[gvanrossum]

It seems that many people try to use --use-python-path because they see some missing imports (e.g. django, see #1410) and then mypy crashes on some random problem. Maybe we shouldn't have --use-python-path at all? @JukkaL, why was it introduced anyway?

[gvanrossum]

UPDATE: I think it was introduced in response to #486 (the diff was 6230e3f by the same user). But I wish it never existed -- people are really better off ignoring imports for which no stubs exist than trying to deal with the errors and crashes from analyzing 3rd party (or stdlib) libraries that haven't been made mypy-clean.

[JukkaL]

I tend to agree that --use-python-path isn't very useful as such. If #638 was implemented (ignoring errors in library modules) and mypy hardly ever crashed, it might be useful, but currently it's unlikely to be helpful. Let's just remove it?