After updating to mongoDB v.2.6 I've started to encounter this error:

```
pymongo.errors.OperationFailure: command SON([('createIndexes', 'fs.chunks'), ('indexes', [

{'name': 'files_id_1_n_1', 'unique': True, 'key': SON([('files_id', 1), ('n', 1)])}

])]) failed: Index with name: files_id_1_n_1 already exists with different options
```

everywhere.

Pymongo driver tries to ensure index at many places (at saving time, at deleting time and so on). And in mongoDB 2.6 something had changed (they removed possibilty to create (some) indexes in background?!).

Now usage if GridFS in pymongo is completely broken.
I had to comment out every line with:

```self._ensure_index()```

to run my code.