Make string formatting work on RHEL6 python 2.6

$ python
Python 2.6.6 (r266:84292, Nov 21 2013, 10:50:32)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-4)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> "{} {}".format('hello', 'world')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: zero length field name in format
>>> "{0} {1}".format('hello', 'world')
'hello world'