error message for failed decision task

error.yml

metadata:
  name: 'Error Message Task'
  description: |
    There was an error creating the decision task.
  owner: "{{owner}}"
  source: "{{{source}}"

tasks:
    taskId: '{{#as_slugid}}decision-task{{/as_slugid}}'
    task:
      created: '{{now}}'
      deadline: '{{#from_now }}5 minutes{{/from_now}}'
      metadata:
        source: '{{{source}}}'
        owner: '{{owner}}'
        name: Error message...
        description: |
          Error creating decision task...

      workerType: gecko-decision
      provisionerId: aws-provisioner-v1
      routes:
         - "tc-treeherder-stage.{{project}}.{{revision_hash}}"
         - "tc-treeherder.{{project}}.{{revision_hash}}"
      payload:
        image: 'quay.io/mozilla/decision:0.0.3'
        maxRunTime: 500
        command:
          - /bin/bash
          - -c
          - >
            echo "[taskcluster:error] ERROR Generating task graph (no tests/build will be created)";
            echo "[taskcluster:error] $ERROR_MSG";
            exit 1
      extra:
        treeherder:
          symbol: D