Convert Python 2.7 statement to its 2.6 equivalent

Just ran into a Python version incompatibility. The production server is
running 2.6 and not 2.7. For now it was easier to simply update this
line of code.

Signed-off-by: Konrad Reiche <konrad.reiche@fokus.fraunhofer.de>
Merge branch 'master' of github.com:fraunhoferfokus/ckanext-govdatade

Signed-off-by: Konrad Reiche <konrad.reiche@fokus.fraunhofer.de>

Conflicts:
	ckanext/govdatade/util.py