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Depending on the user's permissions, this code can hang, instead of raising an exception:
 from tempfile import NamedTemporaryFile
 NamedTemporaryFile(dir="/")
The problamatic code is in tempfile.py:
When encountering a "[Errno 13] Permission denied: '/tmpmcupmo_g'", the current code uses _os.access(dir, _os.W_OK) in two places to check if access is allowed to write to the directory.
On windows, _os.access does not check if the user has permission to write to the folder, it only checks if the folder is read-only (and it doesn't even do a good job at that).
So the temp file creator loops for a rather long time, and consumes a massive amount of system resources, because os.TMP_MAX on modern windows versions is 2147483647.
This article explains how to check if a directory can-write without trying to write to it:
http://blog.aaronballman.com/2011/08/how-to-check-access-rights/
Alternatively, a more careful check of the winerror return value from the open call *might* be sufficient.

Perhaps a duplicate of Issue 22107?

yes, duplicate of https://bugs.python.org/issue22107 ... tried looking first, sry.