# LaurentPolynomial can't factor constants

Hi all,

Many `LaurentPolynomials`

throw errors when I try to factor them. For example:

```
sage: R.<x,y> = LaurentPolynomialRing(QQ)
sage: R.one().factor()
AttributeError: ...
sage: (x^-1).factor()
AttributeError: ...
```

This seems to come from the unit part of `Polynomial.factor()`

sometimes (incorrectly) living in `Integer Ring`

, and sometimes (correctly) living in whatever `self.parent()`

is.

Is this intentional or a bug?

Thanks,

Henry