Wrong wrap of raise expressions when line is too long

this:

```py
raise NotImplementedError(
    'The SimpleListFilter.lookups() method must be overridden to '
    'return a list of tuples (value, verbose value).'
)
```
gets converted to 
```py
raise 
NotImplementedError('The SimpleListFilter.lookups() method must be overridden to '
    'return a list of tuples (value, verbose value).'
)
```