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In 2.6 a deprecation warning was added if `object.__new__` was called
with arguments. Per se this is fine, but the detection seems to be faulty.
The following code shows the problem:
>>> class A(object):
... def __new__(self):
... raise TypeError('i do not exist')
... 
>>> class B(A):
... __new__ = object.__new__
... def __init__(self, x):
... self.x = x
... 
>>> B(1)
__main__:1: DeprecationWarning: object.__new__() takes no parameters
<__main__.B object at 0x88dd0>
In the `B` case `__new__` is not overridden (in the sense that it
differs from object.__new__) but `__init__` is. Which is the default
behaviour. Nonetheless a warning is raised.
I used the pattern with the "__new__ switch" to achieve a
cStringIO.StringIO behavior that supports typechecks: IterIO() returns
either a IterI or IterO object, both instances of IterIO so that
typechecks can be performed.
Real-world use case here:
http://dev.pocoo.org/projects/werkzeug/browser/werkzeug/contrib/iterio.py