[Task] Update python tests to nose #23
Description
What is this task about?
The python tests currently require nose to run, but pytest is a more modern test framework that we use in Cyclus.
Why is this task needed?
We need to keep our tests updated and make it possible for a developer to run them, and to keep them updated for modern architectures.
Relevant resources or references
How can this issue be closed?
Remove nose as a requirement to run the python-based tests, and use pytest as the testing framework.