Get the hashes from the given files

def get_hash_tuple(header_path, cython_path, gen_file_path):
    """Get the hashes from the given files"""

    header_hash = (sha1_of_file(header_path)
                   if os.path.exists(header_path) else 'NA')
    from_hash = sha1_of_file(cython_path)
    to_hash = (sha1_of_file(gen_file_path)
               if os.path.exists(gen_file_path) else 'NA')

    return header_hash, from_hash, to_hash