I am adding lots of single files to my local university's data repository using the python-dvuploader. At some point I always run into the above error. I am circumventing this problem by performing my upload in multiple batches and then closing all open files with psutil after each batch. See the attached python script for the workaround.

I don't know where the error is specifically, but I didn't find a related issue (closed or open) so I imagine this kludge might be helpful for someone else.

upload_to_dataverse.py