List the available_tasks

def list_tasks(collector):
    """List the available_tasks"""
    print("Usage: aws_syncr <environment> <task>")
    print("")
    print("Available environments to choose from are")
    print("-----------------------------------------")
    print("")
    for environment in os.listdir(collector.configuration_folder):
        location = os.path.join(collector.configuration_folder, environment)
        if os.path.isdir(location) and not environment.startswith("."):
            print("\t{0}".format(environment))

    print("")
    print("Available tasks to choose from are:")
    print("-----------------------------------")
    print("")
    keygetter = lambda item: item[1].label
    tasks = sorted(available_actions.items(), key=keygetter)
    sorted_tasks = sorted(list(tasks), key=lambda item: len(item[0]))
    max_length = max(len(name) for name, _ in sorted_tasks)
    for key, task in sorted_tasks:
        desc = dedent(task.__doc__ or "").strip().split('\n')[0]
        print("\t{0}{1} :-: {2}".format(" " * (max_length-len(key)), key, desc))
    print("")