It looks like .10 changed the API for kv. https://www.vaultproject.io/api/secret/kv/kv-v2.html

it now requires /secret/data/path, instead of /secret/path.  The response is also altered, so that you get 

"data":{ 
  "data":{
    "foo": "bar"
  }
} 

vs{{}}

"data": {
    "foo": "bar"
  }

This causes 404 errors if you don't manually put the /data/ into the path, and doesn't allow the key to be found, so you don't get the actual values into the build steps.