Provide useful info when parsing policy file

When parsing the policy.json file we should provide a message that helps
the user or deployer understand there was an issue with the policy file,
and that they should make sure the policy.json file is valid JSON.

Change-Id: I63bdb6d8f03a0510e34b7e10cec25263e7c6c63c
Closes-Bug: #1177623
Merge "Provide useful info when parsing policy file"