Update error text in not.yaml Stack example

Now it matches the RC

Author: david-christiansen

message-index/messages/S-6602/not-yaml/index.md

@@ -5,9 +5,14 @@ title: Not a YAML file
 This `stack.yaml` file is not syntactically valid YAML. The error that results from `stack --stack-yaml not.yaml build` is:
 ```text
 Error: [S-6602]
-Could not parse '/PATH/TO/not.yaml':
-YAML parse exception at line 0, column 0,
-while parsing a block node:
-did not find expected node content
-See http://docs.haskellstack.org/en/stable/yaml_configuration/
+       Stack could not load and parse /PATH/TO/not.yaml as a YAML configuraton file.
+
+       While loading and parsing, Stack encountered the following exception:
+
+       YAML parse exception at line 0, column 0,
+       while parsing a block node:
+       did not find expected node content
+
+       For help about the content of Stack's YAML configuration files, see (for the most recent release of
+       Stack) http://docs.haskellstack.org/en/stable/yaml_configuration/.
 ```