python new test frameworks

Python new test frameworks are required.

I'd like to see some test cases that lead to networks with longer-running iterations, though I understand that there are several factors that might make this difficult.

I had set a limit of t < 10 while developing my solution and was surprised that I passed all of the test cases without making t indefinite.

This kata currently does not explicitly rule out networks with any cycle that contains odd number of -1s, such as

 0 -1 -1
-1  0 -1
-1 -1  0

These networks are unsolvable for obvious reasons, and existing solutions all return their own results when this happens.