egg2dist solicits distinfo_path from two places

[jaraco]

Discovered in pypa/setuptools#1196, it seems that the egg2dist function both accepts a parameter distinfo_path but also accesses self.distinfo_dir. When egg2dist is invoked from an external caller like setuptools, and distinfo_dir isn't set, and the license text functionality is triggered, the function will crash with a TypeError.

egg2dist should either only use distinfo_path passed as a parameter or use the instance attribute. Even better, if possible, egg2dist should be refactored such that it doesn't depend on instance attributes at all (and thus can be a classmethod).

[agronholm]

It should be noted that wheel does not have a public API. If you import wheel code directly, it may break in the next release.

[agronholm]

I'll get this fixed for the next release, if possible. I'm doing a rather large refactoring of the code base now.