Address isinstance python2 and python3 compatibility

[jpcampb2]

Address isinstance python2 and python3 compatibility

[jpcampb2]

The unit tests pass and this issue is at least temporarily resolved. The solution is as follows:

The if isinstance statements in ensure_json_serializable are Python 3 compatible but include a workaround for Python 2 unicode and long types. The else statement includes a try-except block that checks isinstance for unicode and long types. Otherwise, it raises a TypeError indicating that the type cannot be serialized. If the program is being run in Python 3 (and fails the other if statements), the try-except block will raise the TypeError since unicode and long are not valid types in Python 3.

[jpcampb2]

I guess since the feature/unittest_to_pytest branch hasn't been merged into develop yet, this issue should stay open until the merge.

[jpcampb2]

Mission complete