Return the real host for the given WSGI environment.  This takes care
    of the `X-Forwarded-Host` header.

    :param environ: the WSGI environment to get the host of.

def get_host(environ):
    """Return the real host for the given WSGI environment.  This takes care
    of the `X-Forwarded-Host` header.

    :param environ: the WSGI environment to get the host of.
    """
    scheme = environ.get('wsgi.url_scheme')
    if 'HTTP_X_FORWARDED_HOST' in environ:
        result = environ['HTTP_X_FORWARDED_HOST']
    elif 'HTTP_HOST' in environ:
        result = environ['HTTP_HOST']
    else:
        result = environ['SERVER_NAME']
        if (scheme, str(environ['SERVER_PORT'])) not \
           in (('https', '443'), ('http', '80')):
            result += ':' + environ['SERVER_PORT']
    if result.endswith(':80') and scheme == 'http':
        result = result[:-3]
    elif result.endswith(':443') and scheme == 'https':
        result = result[:-4]
    return result