The real problem is that starting with Python2.7, the AssertionError exception is 
created immediately, and as such the tuple survives the code that was use it as 
an argument, so this is a change.

Fix scheduled for next hotfix release.

As found by CPython2.7 test suite, the normalization should also be done for 
"NULL" value, and the wrong exception value creation check, is now covered too.

And another code review result, CPython checks the result from normalization, if 
it really is an exception instance, and complains if it isn't. For compatibility, 
this should be merged too.

Doing code review, I noticed that "tuple exception types" are understood by 
CPython too. It will take the first element of tuples, until it finds a non-tuple 
or empty tuple.

Code for that shall be added too.

Code like this: 

raise AssertionError, (3,)

would create an AssertionError(3), whereas it should be AssertionError((3,)), 
which needs a fix.

The issue is that CPython internally adds the missing tuple-property to 
exception value before calling exception type, except it already has it.

We need to wrap value tuples into one element tuples and it's correct to do it 
for all exception values, then CPython run time doesn't have to do it.