Testing for version to use from __future__ in 2.1

[Daniel Klein]

I've been testing my software using Python version 2.1 with the 'from __future__' statement and I'd
like to be able to release it to users of both 2.1 and 2.0. So I thought to put something like this
as the first line in the module:

if sys.version[:3] == '2.1': from __future__ import nested_scopes

but this returns a (not entirely unexpected) SyntaxError. :-(

Is there anyway (short of maintaining 2 versions) to 'have my cake and eat it too', as this line
would be the only difference betwixt versions of my software.

Thanks,
Daniel Klein