Consider the following, which works:
sage: R.<x> = Integers(4)[]
sage: Q.<a> = R.quotient(x^2)
sage: for q in Q:
....: q
....:
0
1
2
3
a
a + 1
a + 2
a + 3
2*a
2*a + 1
2*a + 2
2*a + 3
3*a
3*a + 1
3*a + 2
3*a + 3
Now if I add a generator to the ideal and execute
sage: Q.<a> = R.quotient((x^2,2*x))
sage: for q in Q:
....: q
....:
I get an error:
NotImplementedError: object does not support iteration
How can I make it work?