In Python 2.2.3 there's a problem with accidental 
subclassing from a Python module, e.g.

import MyStuff

class A(MyStuff):
     pass

this gives no error until you try to instantiate the
class:

o = A()

TypeError: 'module' object is not callable

In Python 2.3 the error is generated at module 
startup time:

class A(MyStuff):
     pass
TypeError: function takes at most 2 arguments (3 given)

Since it is rather common that you create modules which
have the same name as their most important class, I
would find it more appropriate to raise a TypeError
with a message "can't subclass a module instance"
in both versions.

In 2.5, the message says "module.__init__() takes at most 2 arguments (3
given)", which is at least a bit more specific.

You get similar errors when "deriving" from other arbitrary objects, so
I don't know if a special case makes sense here.

I agree. Python can't stop the developer from doing stupid things. We
could remove Py_TPFLAGS_BASETYPE from the module type but that could
cause incompatibilities with existing code.

I'm assigning the bug to our beloved dictator to ask for his opinion.

I don't see an issue to be fixed here; adding special tests in order to
provide more detailed error messages is rarely a good idea.

Also, PEP 8 has said for years now that modules should *not* be named
the same as classes.  Yes, there are a few such modules in the standard
library.  They're historical mistakes that will be fixed in 3.0.