pypy3 actually took over the terse exceptions, but without the conditions.  They'd also need error codes from libmpdec now.

>>>> huge = Decimal('9' * 99)
>>>> huge.quantize(Decimal('0.1'))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/stefan/tmp/pypy3-v6.0.0-linux64/lib_pypy/_decimal.py", line 842, in quantize
    workctx._ctx, status_ptr)
  File "/home/stefan/tmp/pypy3-v6.0.0-linux64/lib_pypy/_decimal.py", line 1631, in __exit__
    self.context._add_status(status)
  File "/home/stefan/tmp/pypy3-v6.0.0-linux64/lib_pypy/_decimal.py", line 1263, in _add_status
    raise exception
decimal.InvalidOperation