SConstruct : Fix documentation build
SConstruct : Fix documentation build

Sphinx needs the pytz module, so we need to search for that too. This hadn't been necessary until now for some reason, but on a new Mac with a fresh install via `pip`, pytz seems to be located somewhere else than it was before.

ivanimanishi/gaffer,ImageEngine/gaffer,lucienfostier/gaffer,johnhaddon/gaffer,ImageEngine/gaffer,lucienfostier/gaffer,lucienfostier/gaffer,GafferHQ/gaffer,hradec/gaffer,hradec/gaffer,boberfly/gaffer,johnhaddon/gaffer,GafferHQ/gaffer,ImageEngine/gaffer,hradec/gaffer,ivanimanishi/gaffer,lucienfostier/gaffer,johnhaddon/gaffer,hradec/gaffer,GafferHQ/gaffer,appleseedhq/gaffer,appleseedhq/gaffer,andrewkaufman/gaffer,boberfly/gaffer,johnhaddon/gaffer,andrewkaufman/gaffer,appleseedhq/gaffer,andrewkaufman/gaffer,hradec/gaffer,ivanimanishi/gaffer,GafferHQ/gaffer,boberfly/gaffer,appleseedhq/gaffer,ivanimanishi/gaffer,andrewkaufman/gaffer,ImageEngine/gaffer,johnhaddon/gaffer,andrewkaufman/gaffer,boberfly/gaffer,GafferHQ/gaffer