LGTM.com - false positive - File is opened but is not closed.

**Description of the false positive**

I may be missing a corner case, but as far as I can see, the file is closed as soon as it is opened:
```python
open(fname, 'wt').close()
```

**URL to the alert on the project page on LGTM.com**

https://lgtm.com/projects/g/numpy/numpy/snapshot/6152182e731afcc49e6ff6c657dcd805619bca56/files/numpy/lib/npyio.py?sort=name&dir=ASC&mode=heatmap#x8b66861ed625e5d3:1