I would probably have written this as:

```python
for str in ['Firefox 24.0b', 'WebappRuntime 24.0b']:
    if str in top_crashers[idx].product_version_label:
        pytest.xfail('Bug 913126 - Advanced Search: No results returned for 24.0b')
```

The effect would be the same, so this is just a case of style. Also, I'm assuming this is a temporary xfail, so in that case it looks fine to me!