Fix exit code of validate-templates script
Fix exit code of validate-templates script

We didn't propagate the error properly in validate-templates, thus
exiting with 0 even when an error happened. We could also get a None
value when parsing environment files.

Change-Id: I005b1491c82db9d389b6176125563811ab2c83ba

andxeg/heat-templates,andxeg/heat-templates,rdo-management/heat-templates,tgreenyc/heat-templates,kwrobert/heat-templates,chrishultin/heat-templates,wesparish/heat-templates,bbandaru/heat-templates,kwrobert/heat-templates,bbandaru/heat-templates,wesparish/heat-templates,chrishultin/heat-templates,rdo-management/heat-templates,bbandaru/heat-templates,wesparish/heat-templates,rdo-management/heat-templates,rdo-management/heat-templates,cosminmocan/heat-templates,chrishultin/heat-templates,rdo-management/heat-templates,wesparish/heat-templates,andxeg/heat-templates,cosminmocan/heat-templates,andxeg/heat-templates,cosminmocan/heat-templates,tgreenyc/heat-templates,chrishultin/heat-templates,tgreenyc/heat-templates,varunarya10/heat-templates,openstack/heat-templates,bbandaru/heat-templates,varunarya10/heat-templates,openstack/heat-templates,cosminmocan/heat-templates,kwrobert/heat-templates,kwrobert/heat-templates,openstack/heat-templates,tgreenyc/heat-templates