Typo checks in core.ops
https://github.com/pandas-dev/pandas/blob/master/pandas/core/ops.py#L490

```
            elif (isinstance(ovalues, datetime.datetime) and
                  hasattr(ovalues, 'tzinfo')):
```

Is that `hasattr(ovalues, 'tzinfo')` supposed to be `ovalues.tzinfo is not None`?