### Quotienting a ring of integers

I was trying to play within the ring of integers of a number field, when I decided to quotient by an ideal. It raised an "IndexError: the number of names must equal the number of generators" exception, which was quite unexpected ; here is an example:

```
K=NumberField(x**2+1,x)
O=K.ring_of_integers()
O.quo(O.ideal(3))
```

as you see, I'm using the same ring to define the ideal I want to quotient with, so there is mathematically no problem... so I think either I found a bug or something needs to be documented better. How does one work in a quotient of a ring of integers?