def find_default_vpc(session, region_name):
    """
    Looks for every default VPC in a region
    :param session: Boto3 Session
    :param region_name: The region name to look in
    :return: list of vpc id's
    """
    result = []
    client = session.client("ec2", region_name)
    response = client.describe_vpcs(
        Filters=[{
           'Name': 'isDefault',
           'Values': ['true']
        }]
    )

    for vpc in response['Vpcs']:
        if vpc['IsDefault']:
            result.append(vpc['VpcId'])

    return result