fix.txt

Original error happens on line 11, that exit_ok was default to be False which caused the file_exist erorr, I made the change to set it to be True.
Also added a docstring for the download_file function.

sample.py

import os
import urllib.request
from urllib.parse import urlparse


def download_file(url, cachedir=None, ignorecache=False, filename=None) -> str:
"""download_file would create a directory if not exist, then download the file to directory, it accept url, target directory, whether or not ignore existed file, and filename as arguments, it returns the path of the new directory."""
    if not cachedir:
        cachedir = os.path.join(os.getcwd(), "build")

    os.makedirs(cachedir,exit_ok=True)

    if not filename:
        filename = os.path.basename(urlparse(url).path)

    path = os.path.join(cachedir, filename)
    
    if ignorecache or not os.path.exists(path):
        urllib.request.urlretrieve(url, path)

    return path
    
if __name__ == "__main__":
dlpath = download_file("http://pantry.learningequality.org/downloads/ka-lite/0.16/content/contentpacks/en.zip")