Replace use of tempnam, which is unavailable on App Engine
Replace use of tempnam, which is unavailable on App Engine

There is a chance of a collision if files with the same name are uploaded at
the same time to the nearest microsecond. However, sadly, the server already
has other issues that would cause it to error before this could ever be an
issue.

jcfr/Midas,jcfr/Midas,jcfr/Midas,jcfr/Midas,jcfr/Midas,jcfr/Midas