Ataki/gridfs

@stvstnfrd to review commit
Lets use keyword args instead of positional args here:
```
File {size} exceeds...
```
This is important because when translators l10n this message, they won't
have context for what the positional argument `%s` is, whereas `{size}`
will provide better context. Also, the order of args can change depending
on the target language.