I thought that I would fix gihub bug #22313 (Implement Euler Polynomials)

So I added a function (boiled down, the implementation here is obviously incorrect)

```
def euler_polynomial(x, n):
r"""
Compute the value of the ``n``-th Euler polynomial at ``x``.
TESTS::
sage: y=QQ['y'].gen()
sage: euler_polynomial(y, 0)
1
"""
return 1
```

Now if I run `./sage -t src/sage/combinat/combinat.py`

I get

```
[...]
File "<doctest sage.combinat.combinat.euler_polynomial[1]>", line 1, in <module>
euler_polynomial(y, Integer(0))
^^^^^^^^^^^^^^^^
NameError: name 'euler_polynomial' is not defined
**********************************************************************
1 item had failures:
1 of 3 in sage.combinat.combinat.euler_polynomial
[462 tests, 1 failure, 2.38 s]
```

I am obviously doing something wrong, but am at a loss as to what. I have tried rebuilding sage.