this style of formatting is not supported in python2.6
```python
In [5]: '{}({})'.format('sorry', '>= 2.7 only')
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-5-b84304fedd68> in <module>()
----> 1 '{}({})'.format('sorry', '>= 2.7 only')

ValueError: zero length field name in format
```