'Add additional requirements from setup.cfg to file metadata_path'

def add_requirements(self, metadata_path):

    additional = list(self.setupcfg_requirements())
    if (not additional):
        return
    pkg_info = read_pkg_info(metadata_path)
    if (('Provides-Extra' in pkg_info) or ('Requires-Dist' in pkg_info)):
        warnings.warn('setup.cfg    requirements    overwrite    values    from    setup.py')
        del pkg_info['Provides-Extra']
        del pkg_info['Requires-Dist']
    for (k, v) in additional:
        pkg_info[k] = v
    write_pkg_info(metadata_path, pkg_info)
