Prepares the given HTTP URL.

def prepare_url(self, url, params):
        """Prepares the given HTTP URL."""
        url = to_native_string(url)

        # Don't do any URL preparation for non-HTTP schemes like `mailto`,
        # `data` etc to work around exceptions from `url_parse`, which
        # handles RFC 3986 only.
        if ':' in url and not url.lower().startswith('http'):
            self.url = url
            return

        # Support for unicode domain names and paths.
        scheme, auth, host, port, path, query, fragment = parse_url(url)

        if not scheme:
            raise MissingSchema("Invalid URL {0!r}: No schema supplied. "
                                "Perhaps you meant http://{0}?".format(url))

        if not host:
            raise InvalidURL("Invalid URL %r: No host supplied" % url)

        # Only want to apply IDNA to the hostname
        try:
            host = host.encode('idna').decode('utf-8')
        except UnicodeError:
            raise InvalidURL('URL has an invalid label.')

        # Carefully reconstruct the network location
        netloc = auth or ''
        if netloc:
            netloc += '@'
        netloc += host
        if port:
            netloc += ':' + str(port)

        # Bare domains aren't valid URLs.
        if not path:
            path = '/'

        if is_py2:
            if isinstance(scheme, str):
                scheme = scheme.encode('utf-8')
            if isinstance(netloc, str):
                netloc = netloc.encode('utf-8')
            if isinstance(path, str):
                path = path.encode('utf-8')
            if isinstance(query, str):
                query = query.encode('utf-8')
            if isinstance(fragment, str):
                fragment = fragment.encode('utf-8')

        enc_params = self._encode_params(params)
        if enc_params:
            if query:
                query = '%s&%s' % (query, enc_params)
            else:
                query = enc_params

        url = requote_uri(urlunparse([scheme, netloc, path, None, query, fragment]))
        self.url = url