Some web server configurations prevent uploading of files with suspicious types

(like .cgi, .php, etc). In this case, the security checklist would throw a 500

because it would fail to even save the file, much less fetch it.
I've rearranged things a little bit to catch OSError exceptions when saving

files and remove them from the list of things that we then test/delete.

Manually caused one of the file types to throw an OSError and saw that the

security checks still passed.