I was thinking about that -- we could use `OPENID_SSO_SERVER_URL`, but that name doesn't convey the the need to replace something in the string. I don't know how important the `FMT` suffix is, as long as we update docs to mention that a formatting field can be used. We'll also have to add a check for a formatting field before we blindly assign the `OPENID_SSO_SERVER_URL` to the `openid_url`. Something kind of gross for now, like:

```python
try:
    openid_url = OPENID_SSO_SERVER_URL % request.GET['hd']
except TypeError:
    # Must not have had a formatting field
    pass
```

Am I even in the ballpark of what you're asking?