A shorter way of doing the optional plural i've seen often is:

```python
message = "[%s]  Retrieving model%s ... " % (get_date(), "s"[len(model_ids)==1:], ...)
```

I would perhaps define a function in `util`, so you can reuse it:

```python
def plural(text, num):
    return "%s%s" % (text, "s"[num==1:])
```