Eventually matcher should catch exceptions on the callable

With the current implementation of eventually, if the callable passed as the first argument raises an exception, it will be propagated and the assertion will fail.

I was expecting eventually to catch this exception and keep retrying until it times out. And just at this moment raise the exception.

This is the statement I would like to use:

self.assertThat(
            fake_url_dispatcher.get_last_dispatch_url_call_parameter,
            Eventually(Equals('settings:///system/online-accounts')))

get_last_dispatch_url_call_parameter raises an exception if URL dispatcher hasn't been called. It's eventually called, and then returns the value.

As a workaround, I had to wrap it in a function that catches the exception and returns None. This doesn't seem correct, because then I can't test for cases when the parameter passed to the fake service is None.