Ø character in preview file name causes upload to hang

[ocaisa]

Describe the bug
We found out today is that if the filename of a preview file has a ø character it causes the upload of the preview file to hang with no output. This was with PyClowder 2.7.0.

I'd suspect this is also true for other utf8 characters.

To Reproduce
Steps to reproduce the behavior:

1. Try to upload a preview file using PyClowder which has a ø character in the filename

Expected behavior
Accept any valid filename.

Additional context
I was using the name of a dataset as the file name for video preview. The code already uses the pathvalidate module on that name. For now I've added a filter to remove any non-alphanumeric characters.