I tried running the vntnt.py file in the windows command prompt in the file directory, with 2 folders for the input and output of the vnt files.
The folder that had the .vnt files was named 'vnts', and had 40 .vnt files with the names unchanged from when they were copied from the android phone.
The output folder was named 'outputvnt', and they were both in the same directory as the vntnt.py file.
I wrote this in the command prompt in the file directory:
"python vntnt.py vnts outputvnt" (without the quotes) and it gave me this output:
Traceback (most recent call last):
File "vntnt.py", line 96, in
convertNote(fullFileName, outputDir)
File "vntnt.py", line 73, in convertNote
note.write(outFilename)
File "vntnt.py", line 64, in write
file = codecs.open(filename, "w", "utf-8")
File "C:\Python27\lib\codecs.py", line 881, in open
file = builtin.open(filename, mode, buffering)
IOError: [Errno 22] invalid mode ('wb') or filename: 'outputvnt\2019-01-02T10:08:55.txt'
I think it is probably having trouble with the name string, maybe because it has colons in it, and windows does not allow naming of files with colons in the name. I think this problem could probably be fixed by removing colons from the output file name, or maybe naming the file something else than the date and time in the .vnt file.

I think it is probably just a problem with naming the file because that is what the error message looks like it has a problem with, but I might be wrong and it isn't actually trying to name it with colons, and it means somehthing else, because I don't understand or use python very much.