Makes the already-existing environment use relative paths, and takes out
    the #!-based environment selection in scripts.

def make_environment_relocatable(home_dir):
    """
    Makes the already-existing environment use relative paths, and takes out
    the #!-based environment selection in scripts.
    """
    home_dir, lib_dir, inc_dir, bin_dir = path_locations(home_dir)
    activate_this = os.path.join(bin_dir, 'activate_this.py')
    if not os.path.exists(activate_this):
        logger.fatal(
            'The environment doesn\'t have a file %s -- please re-run virtualenv '
            'on this environment to update it' % activate_this)
    fixup_scripts(home_dir, bin_dir)
    fixup_pth_and_egg_link(home_dir)