Got error when running

[hautph]

Traceback (most recent call last):
File "main.py", line 61, in
print(upload_files(bucketName))
File "main.py", line 22, in upload_files
files = [f for f in listdir(localFolder) if isfile(join(localFolder, f))]
File "main.py", line 22, in
files = [f for f in listdir(localFolder) if isfile(join(localFolder, f))]
File "/usr/lib64/python3.6/posixpath.py", line 80, in join
a = os.fspath(a)
TypeError: expected str, bytes or os.PathLike object, not NoneType