def _build_url(url, _params):
    """Build the actual URL to use."""

    # Support for unicode domain names and paths.
    scheme, netloc, path, params, query, fragment = urlparse(url)
    netloc = netloc.encode('idna').decode('utf-8')
    if not path:
        path = '/'

    if six.PY2:
        if isinstance(scheme, six.text_type):
            scheme = scheme.encode('utf-8')
        if isinstance(netloc, six.text_type):
            netloc = netloc.encode('utf-8')
        if isinstance(path, six.text_type):
            path = path.encode('utf-8')
        if isinstance(params, six.text_type):
            params = params.encode('utf-8')
        if isinstance(query, six.text_type):
            query = query.encode('utf-8')
        if isinstance(fragment, six.text_type):
            fragment = fragment.encode('utf-8')

    enc_params = _encode_params(_params)
    if enc_params:
        if query:
            query = '%s&%s' % (query, enc_params)
        else:
            query = enc_params
    url = (urlunparse([scheme, netloc, path, params, query, fragment]))
    return url