package_dir must be converted from the distutils path conventions to local conventions before being used by build_py.
package_dir must be converted from the distutils path conventions to
local conventions before being used by build_py.

Fixes SF bug #509288, probably a candidate for 2.2.1

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator