• add some utilities to create pickle diff to check for determinist pickle.
• add some tests to check if the same dynamic class, constructed from scratch or loaded from a cloudpickle stream, leads to the same pickle file:
  • Check for attribute order issues.
  • Check for some string interning issues.

One case seems unsolvable: when updating the class state, all attrname for a class are interned. This is why we are also interning the dynamic func names, to be consistent between their name and the method names (all interned).
But if some values in the pickle stream (anywhere) have the same value as one attrname, then these two strings which are the same in the original pickle file become different in the unpickled objects. Typically, pickling the following original dynamic class results in memorization of join between the method name and the argument value, while pickling the unpickled class leads to no memorization: arg_1 = "join" value is not interned. In contrast, the join method name is.

class A:
    '''Class with potential string interning issues.'''
    arg_1 = "join"

    def join(self, arg_1):
        pass

Not sure if there is a solution for this one.
Note that this test can be run locally with pytest -vv --runxfail -k determinist_subworker_str_interning

Related issues: #510, #453.