No longer silently skip setuptools plugins that raise DistributionNotFound errors

[nicoddemus]

Fix #174

[RonnyPfannschmidt]

it should be noted that this is a breaking api change if applied to pytest as is

[nicoddemus]

Not sure Ronny, I think this is a bug fix,also that api is not really exposed by pytest is it?

[RonnyPfannschmidt]

This bugfix adds New exit points

[nicoddemus]

True. Oh well, this will have to come later then.

[goodboy]

if it's breaking can't we just make it part of pluggy 1.0?

[nicoddemus]

The problem is that it will break pytest, for pluggy this change is fine, as being 0.X you are allowed for backward incompatible changes.

Just realized that one way to move this forward is to instead trigger a warning. This might be even the final solution in the long run. What do you think @RonnyPfannschmidt?

[RonnyPfannschmidt]

lets move the entry-point iteration/loading to a helper that for a grace period will be warning about errors