def METHOD_NAME(hostname='nerscdb03.nersc.gov', username='desidev_admin'):
    """Read a ``~/.pgpass`` file.
    Parameters
    ----------
    hostname : :class:`str`, optional
        Database hostname.
    username : :class:`str`, optional
        Database username.
    Returns
    -------
    :class:`str`
        A string suitable for creating a SQLAlchemy database engine, or None
        if no matching data was found.
    """
    fmt = "postgresql://{3}:{4}@{0}:{1}/{2}"
    try:
        with open(expanduser('~/.pgpass')) as p:
            lines = p.readlines()
    except FileNotFoundError:
        return None
    data = dict()
    for l in lines:
        d = l.strip().split(':')
        if d[0] in data:
            data[d[0]][d[3]] = fmt.format(*d)
        else:
            data[d[0]] = {d[3]: fmt.format(*d)}
    if hostname not in data:
        return None
    try:
        pgpass = data[hostname][username]
    except KeyError:
        return None
    return pgpass