Support the modern METADATA file in extension packages.
Review Request #8068 — Created March 21, 2016 and submitted — Latest diff uploaded
Modern Python packages store metadata in a METADATA file, rather than in a PKG-INFO file. This updates our extension metadata parsing to try this file first, falling back on PKG-INFO. That gives us compatibility with any modern packages (particularly wheels), while retaining support for older packages (eggs).
Tested this with an extension containing a METADATA file but not PKG-INFO.
Successfully extracted metadata from the package for the extension.