If the package name is an empty string (ie the default
package), all package_data files have the first
character chopped off.
Attached is a test package pytest.tar.gz where running
python2.4 setup.py build_py
produces this error:
running build_py
creating build
creating build/lib
copying __init__.py -> build/lib
error: can't copy 'ATA': doesn't exist or not a regular
file

Also attached is a fix proposal, though I have tested
this only against the test package.