Write a proc.yaml for the container and return the container path

def _write_buildproc_yaml(build_data, env, user, cmd, volumes, app_folder):
    """
    Write a proc.yaml for the container and return the container path
    """

    buildproc = ProcData({
        'app_folder': str(app_folder),
        'app_name': build_data.app_name,
        'app_repo_url': '',
        'app_repo_type': '',
        'buildpack_url': '',
        'buildpack_version': '',
        'config_name': 'build',
        'env': env,
        'host': '',
        'port': 0,
        'version': build_data.version,
        'release_hash': '',
        'settings': {},
        'user': user,
        'cmd': cmd,
        'volumes': volumes,
        'proc_name': 'build',
        'image_name': build_data.image_name,
        'image_url': build_data.image_url,
        'image_md5': build_data.image_md5,
    })

    # write a proc.yaml for the container.
    with open('buildproc.yaml', 'w') as f:
        f.write(buildproc.as_yaml())
    return get_container_path(buildproc)