Revert "Handle error with non existing template file"

This is causing the test_stack_update_provider_group functional test
to fail, so revert while we investigate.

This reverts commit 51390e8ba70cc22202e27f972455af66d3dbe779.

Change-Id: I271780f3ac02030dfde9ba9beb8921dc9211c06d
Merge "Revert "Handle error with non existing template file""