IMHO stuffing xxmodule.c inside the distutils test tree (see msg100815) is the right solution because the python source tree might not be present during testing (such as when the user does a binary install and then runs the unittests to check if everything works).

Tarek: sysconfig.get_config_var('srcdir') returns the value of 'srcdir' in  'Makefile' and that value is only valid during the build of Python. It is the variable that is used in Python's makefiles to refer to files in the source tree and is needed when you run configure from a directory that is not the root of the source tree.