The following MWE shows how to get the error message described in the title:

from tqdm import tqdm
from multiprocessing import Pool

def f(arg):
    pass

if __name__ == '__main__':
    pool = Pool()
    list(tqdm(pool.imap(f, range(100)), disable=True))

• tqdm Version: 4.22.0
• python 3.6.0
• Win64

It works, when the disable=True is removed or set to False. But it should also work for the disabled case I would guess.