StubOutWithMock on a MockAnything sometimes succeeds, sometimes fails.

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What steps will reproduce the problem?

1. Create a source file mox_restub.py, with the following contents:

import mox

class MyClass(object):

    def MyFunction():
        pass

m=mox.Mox()

print MyClass.MyFunction    # <unbound method MyClass.MyFunction>

m.StubOutWithMock(MyClass, 'MyFunction')

print MyClass.MyFunction    # <MockAnything instance at 139942970002032>

m.StubOutWithMock(MyClass, 'MyFunction')

print MyClass.MyFunction    # <MockAnything instance at 139942970064208>

m.StubOutWithMock(MyClass, 'MyFunction') 
                            # TypeError: Cannot Mock a MockAnything! Did you
                            # remember to call UnsetStubs in your previous 
                            # test?

2. run python ./mox_restub.py

*****

What is the expected output? What do you see instead?

I expect an exception to be thrown at the second call to StubOutWithMock, since 
MyClass.MyFunction is already a MockAnything that has not been unset with 
UnsetStubs.

Instead, the second call to StubOutWithMock silently succeeds, but the third 
call fails.

*****

What version of the product are you using? On what operating system?

mox: python-mox 0.5.3-1ubuntu5
os:  Ubuntu 12.04.1 LTS

Original issue reported on code.google.com by akes...@google.com on 15 Feb 2013 at 6:42