Add lesscpy>=0.9h

A prereq to drop horizon's less.js (and thus NodeJS) dependency for
compiling static assets.

See https://review.openstack.org/#/c/37473/

Change-Id: I265b35def7cdd20c2d1c1040b7fb788c2f2a3e8f
Merge "Add lesscpy>=0.9h"