def change_root(new_root, pathname):
    """Return 'pathname' with 'new_root' prepended.  If 'pathname' is
    relative, this is equivalent to "os.path.join(new_root,pathname)".
    Otherwise, it requires making 'pathname' relative and then joining the
    two, which is tricky on DOS/Windows and Mac OS.
    """
    if os.name == 'posix':
        if not os.path.isabs(pathname):
            return os.path.join(new_root, pathname)
        else:
            return os.path.join(new_root, pathname[1:])

    elif os.name == 'nt':
        (drive, path) = os.path.splitdrive(pathname)
        if path[0] == '\\':
            path = path[1:]
        return os.path.join(new_root, path)

    raise DistutilsPlatformError(f"nothing known about platform '{os.name}'")
Return 'pathname' with 'new_root' prepended.  If 'pathname' is
    relative, this is equivalent to "os.path.join(new_root,pathname)".
    Otherwise, it requires making 'pathname' relative and then joining the
    two, which is tricky on DOS/Windows and Mac OS.
    
product/gradle-plugin/src/main/python/setuptools/_distutils/util.py