F401 (imported but not used) in __init__.py

[crusaderky]

Virtually every medium to large library package I've encountered so far is structured as follows:

• impl.py defines objects
• __init__.py imports them, so that the library users don't need to know about impl.py.

At the moment, the __init__.py modules of packages that use flake8 are littered with either # noqa: F401 on every single line or # flake8: noqa at the top of the module which blanket disables everything.

This change request is to add a special case in pyflakes that disables F401 (only) when the file name is __init__.py.
An alternative approach would be to add to flake8 the ability to suppress specific errors at module level, e.g. # flake8: noqa: F401.

[asottile]

If you list the things you export in __all__ (a best practice for __init__.py files which export names) you will not need to disable anything -- that marks the names as used

[crusaderky]

When you have a large amount of objects, it's convenient to define __all__ programmatically, which pyflakes doesn't figure out:

__all__ = tuple(k for k in locals() if not k.startswith("_"))

[asottile]

sure, I was just giving the suggestion from the duplicate issue #162