Python mock swallows exceptions

I'm using python mock library (python 2.7, mock==1.0.1) and when mocking out certain parts of code that I'm testing mock is swallowing exceptions for some reason.

Below is an example:

#test.py
from something import main_func
class TestCase(test.TestCase):
  @mock.patch('something.somewhere')
  def test_something(mock_somewhere):
    main_func()


#something.py
def somewhere(param):
  print param

def main_func():
  somewhere(None.missing_something)

So AttributeError should be raised right? This test is passing on my machine, in reality the code is more complicated, a Django Model is supposed to be saved and existing. The test is failing because the model doesn't exist.

If I insert an import ipdb; ipdb.set_trace() just before somewhere(None.missing_method) then I can see the AttributeException is raised but it doesn't show up in the test.

Any ideas?