Detailed error message on hook registration conflict

[vitek]

Hi! I've spent some time trying to nail down hook registration error:

INTERNALERROR>     pluginmanager.add_hookspecs(Hookspec)
INTERNALERROR>   File "contrib/python/pluggy/py3/pluggy/_manager.py", line 175, in add_hookspecs
INTERNALERROR>     hc.set_specification(module_or_class, spec_opts)
INTERNALERROR>   File "contrib/python/pluggy/py3/pluggy/_hooks.py", line 200, in set_specification
INTERNALERROR>     assert not self.has_spec()
INTERNALERROR> AssertionError

This PR raises RuntimeError with detailed message which should ease developer's life a bit:

E           RuntimeError: Hook 'conflict' is already registered within namespace <class 'test_hookcaller.test_hook_conflict.<locals>.Api1'>

src/pluggy/_hooks.py:341: RuntimeError

[RonnyPfannschmidt]

Thank you for getting this started, the pr is well prepared.

Please have a look at my comments.

[RonnyPfannschmidt]

This ough to be a ValueError or a subclass of it

[RonnyPfannschmidt]

Please add a check for the message, just to be safe

[RonnyPfannschmidt]

Well done, would you like to compact history or squash?

[vitek]

I usually do squash on merge. Should I do it myself?

[RonnyPfannschmidt]

We currently don't have squash merge enabled on the repo, but of you consent to squash I'll happily do it later today after enabling

[nicoddemus]

LGTM, would you like to add a CHANGELOG entry as well?

[vitek]

LGTM, would you like to add a CHANGELOG entry as well?

No thank you, it's minor fix. Still can add line if it's required.

[bluetech]

Thanks!