def ensure_protocol(url):
    """Fixes missing URL protocols.

    Adds an appropriate HTTP protocol to the given URL if it is missing.

    :Parameters:
      - `url`: The URL to fix

    :Returns:
      The fixed URL. If the protocol exists, it returns the original URL.
    """
    if not url.startswith('http://') and not url.startswith('https://'):
        return 'http://{}'.format(url)
    else:
        return url
