>>> bool(trap)
False

>>> with ExceptionTrap(ValueError) as trap:
...     raise ValueError("1 + 1 is not 3")
>>> bool(trap)
True
>>> trap.value
ValueError('1 + 1 is not 3')
>>> trap.tb
<traceback object at ...>

>>> with ExceptionTrap(ValueError) as trap:
...     raise Exception()
Traceback (most recent call last):
...
Exception

>>> bool(trap)
False
)