ELB and ELBV2 (Classic and Application load balancers) use the same
    hostname and url space. To differentiate them we must read the
    `Version` parameter out of the url-encoded request body. TODO: There
    has _got_ to be a better way to do this. Please help us think of
    one.

def api_version_elb_backend(*args, **kwargs):
    """
    ELB and ELBV2 (Classic and Application load balancers) use the same
    hostname and url space. To differentiate them we must read the
    `Version` parameter out of the url-encoded request body. TODO: There
    has _got_ to be a better way to do this. Please help us think of
    one.
    """
    request = args[0]

    if hasattr(request, 'values'):
        # boto3
        version = request.values.get('Version')
    elif isinstance(request, AWSPreparedRequest):
        # boto in-memory
        version = parse_qs(request.body).get('Version')[0]
    else:
        # boto in server mode
        request.parse_request()
        version = request.querystring.get('Version')[0]

    if '2012-06-01' == version:
        return ELBResponse.dispatch(*args, **kwargs)
    elif '2015-12-01' == version:
        return ELBV2Response.dispatch(*args, **kwargs)
    else:
        raise Exception("Unknown ELB API version: {}".format(version))