Set output for the error message (#446)

* Set output for the error message

In the event vault-action throws an error, the error message is
sent to the workflow log when with core.setFailed, but that output
is not accessible to other steps in the workflow.

This change sets an output for the error message, called errorMessage,
than can be read by other steps within the workflow and parsed.

* Add hashicorp/vault-action#446 to improvements in CHANGELOG

CHANGELOG.md

@@ -3,6 +3,7 @@
 Features:
 
 * Added support for userpass and ldap authentication methods [GH-440](https://github.com/hashicorp/vault-action/pull/440)
+* Define an output, `errorMessage`, for vault-action's error messages so subsequent steps can read the errors [GH-446](https://github.com/hashicorp/vault-action/pull/446)
 
 ## 2.5.0 (Jan 26th, 2023)
 

src/entry.js

@@ -5,6 +5,7 @@ const { exportSecrets } = require('./action');
     try {
         await core.group('Get Vault Secrets', exportSecrets);
     } catch (error) {
+        core.setOutput("errorMessage", error.message);
         core.setFailed(error.message);
     }
 })();