Using python's mock to temporarily delete an object from a dict

I am writing a test for some code that checks for a value in os.environ (I know this isn't optimal, but I have to go with it). I would like to remove an entry from os.environ for the duration of the test. I am not sure if mock supports this. I know patch.dict can be used to modify an item, but I want the key/value pair removed. I would like something along these lines:

print os.environ
{ ... , 'MY_THING': 'foo', ... }

with mock.patch.dict.delete('os.environ', 'MY_THING'):
    # run the test
    # ( 'MY_THING' in os.environ ) should return False

# everything back to normal now    
print os.environ
{ ... , 'MY_THING': 'foo', ... }

Is there a way to perform such a feat?