Update unit test testing docker environment from Python 2 to Python 3

[dhblum]

Currently, some unit tests (e.g. test_parser, test_data) are run within the jm docker container environment. This used to be the same as the boptest test case docker container. After #146, the test case container uses Python 3, and so the testing environment for these elements should replicate that to avoid needing to use syntax compatible with Python 2 in the framework in order to pass tests.