I did try that initially.

default=None doesn't seem to denote a fallback value.

```Python
(Pdb) self.REQUEST
*** AttributeError: C instance has no attribute 'REQUEST'
(Pdb) from Acquisition import aq_acquire
(Pdb) aq_acquire(self, 'REQUEST', default=None)
*** AttributeError: C instance has no attribute 'REQUEST'
```