def _build_backend():
    """Find and load the build backend"""
    ep = os.environ['PEP517_BUILD_BACKEND']
    mod_path, _, obj_path = ep.partition(':')
    try:
        obj = import_module(mod_path)
    except ImportError:
        raise BackendUnavailable
    if obj_path:
        for path_part in obj_path.split('.'):
            obj = getattr(obj, path_part)
    return obj
Find and load the build backend
stackoverflow/venv/lib/python3.6/site-packages/pip-19.0.3-py3.6.egg/pip/_vendor/pep517/_in_process.py