Allow a package to resolve its own resources simply

[jaraco]

Fixes#259.

[jaraco]

An issue I found with this implementation is that a call to files(__main__) will result in an error because __main__.__spec__ is None... and while it's not common to call files(__main__) or files('__main__'), it would probably not be uncommon for someone to call files() from __main__.

[jaraco]

An issue I found with this implementation is that a call to files(__main__) will result in an error because __main__.__spec__ is None... and while it's not common to call files(__main__) or files('__main__'), it would probably not be uncommon for someone to call files() from __main__.

I'm tempted to explicitly support __main__ to make that use-case easy and congruent to others.

[jaraco]

I'm tempted to explicitly support __main__ to make that use-case easy and congruent to others.

In the latest patch, I'm no longer able to replicate this issue, so I'm declaring it a non-issue:

 importlib_resources feature/implicit-here $ cat foo.py
import importlib_resources as res
def main():
print(res.files())
__name__ == '__main__' and main()
importlib_resources feature/implicit-here $ .tox/python/bin/python -m foo
/Users/jaraco/code/python/importlib_resources