File/Folder names with invalid characters break the script

[pakshuang]

Thanks for creating this script, it's really useful!

However, I seem to be experiencing issues on Windows when the file/folder names contain invalid characters such as colons. https://docs.microsoft.com/en-sg/windows/win32/fileio/naming-a-file#naming-conventions

- C:\Users\paksh\Documents\luminustest\SP1541-ES1541\Submission Folder:  Pre-course Writing Task\SP1541_AY2122Sem2_PreCourseWritingTask_SubmissionTemplate.docx
Traceback (most recent call last):
  File "C:\Users\paksh\Documents\GitHub\pyfluminus\pyfluminus_cli.py", line 109, in <module>
    download_files(module_file, auth, args.download_to, True)
  File "C:\Users\paksh\Documents\GitHub\pyfluminus\pyfluminus_cli.py", line 36, in download_files
    download_files(child, auth, download_path, verbose)
  File "C:\Users\paksh\Documents\GitHub\pyfluminus\pyfluminus_cli.py", line 36, in download_files
    download_files(child, auth, download_path, verbose)
  File "C:\Users\paksh\Documents\GitHub\pyfluminus\pyfluminus_cli.py", line 27, in download_files
    file.download(auth, download_path, verbose)
  File "C:\Users\paksh\Documents\GitHub\pyfluminus\pyfluminus\structs.py", line 314, in download
    return utils.download(url, destination, verbose)
  File "C:\Users\paksh\Documents\GitHub\pyfluminus\pyfluminus\utils.py", line 26, in download
    os.makedirs(dir_path, exist_ok=True)
  File "C:\Users\paksh\AppData\Local\Programs\Python\Python39\lib\os.py", line 225, in makedirs
    mkdir(name, mode)
NotADirectoryError: [WinError 267] The directory name is invalid: 'C:\\Users\\paksh\\Documents\\luminustest\\SP1541-ES1541\\Submission Folder:  Pre-course Writing Task'

It works fine on Linux systems though, I discovered this issue because I run this script on my linux server and sync the files to my Windows laptop, but the sync wasn't working for certain folders with naming issues.