Bug in enum test cases: schema can't handle int

[RunOrVeith]

The tests inside test_enum.TestValidator have relied on a wrong operator binding order and thus
two cases that are actually not valid marshmallow were tested to be valid.

The issue is the following line:

assert not res == is_valid

res here is the output of schema.validate(), which returns a dict of validation errors.

However, not as lower precedence than == (see here), so the statement was treated as

assert not (res == is_valid)

which was Trueno matter what, since we compared a dict to a bool.

After fixing the precedence, two test cases fail: TestValidator.test_data_with_enum (1, True) and (1.23, True), because marshmallow does in fact not allow int enum values (there is a marshmallow_enum in the ecosystem here).

I will enclose a pull request that tests that these cases are actually False.
I found this while implementing a feature that allows enums as dict keys, which I will also link.
@lidatong