Making AssertError a singleton

[Andrei Alexandrescu via Digitalmars-d]

On 12/12/16 4:35 PM, Brad Roberts via Digitalmars-d wrote:
> Of course, then you'll find the fun of all the tests (and probably code)
> that catch AssertError.

You can catch AssertError. There's no guarantees dtors have been called 
during unwinding. -- Andrei