Use 'usedforsecurity' flag when using hashing functions for non-security purposes

[djhoese]

We occasionally use python's hashlib to generate hashes for things like AreaDefinitions. On FIPS-enabled systems, certain hashing algorithms are disabled from use for security reasons. This is common in certain US government organizations. It turns out there is a feature in some versions of Python to say "I know I'm using md5sum and it is not well-suited for security purposes, but I'm not using it for security" by passing a usedforsecurity=False keyword argument to some of the hashing functions. See it discussed here:

https://stackoverflow.com/questions/54717862/how-do-i-know-if-the-usedforsecurity-flag-is-supported-by-hashlib-md5