This simplifies the changes, reduces the scope of refactors apparently
for refactoring's sake and ensures that the internals are reasonable.
It also airs on the side of preserving information rather than
discarding or overwriting it.
Previously, pycodestyle never introspected the argument names for
classes except to require that ``tree`` be an argument it could pass.
For Flake8 3.0, we lifted that restriction, but old plugins seem to
have cargo-culted their __init__ signature to be
def __init__(self, tree, builtins=None):
For some yet unknown reason. This was causing an AttributeError. By
updating flake8.utils.parameters_for to return a dictionary that
indicates whether the parameter is required or not, we can side-step
this by simply ignoring the parameter if it has a default value and
we cannot provide it.
Closes#151
