Message 63475 - Python tracker

distutils.sdist.add_defaults adds the Python modules and scripts and C
extensions found in setup.py to the MANIFEST.  It does *not* add
data_files mentioned in setup.py to the MANIFEST.

This is non-orthogonal and confusing, because it means that a
MANIFEST.in is required if you have data_files, optional if you do not.
 If you have data_files and do not have MANIFEST.in, you get a broken
package but no error.