Fix Automation triggered by scheduler

  <extension target="org.nuxeo.ecm.core.scheduler.SchedulerService"
      point="schedule">
    <schedule id="stuff">
      <username>Administrator</username>
      <eventId>doStuff</eventId>
      <eventCategory>default</eventCategory>
      <cronExpression>0/30 * * * * ?</cronExpression>
    </schedule>
  </extension>

function run(input, params) {
  Auth.LoginAs(null, {});
  var query = "SELECT * FROM Document WHERE ecm:primaryType = 'CommentExpiry' '";
  var subDocs = Document.Query(null, {
    "query": query
  }
}

Caused by: org.nuxeo.ecm.core.api.NuxeoException: cannot find core session
	at org.nuxeo.ecm.platform.query.nxql.CoreQueryDocumentPageProvider.getCoreSession(CoreQueryDocumentPageProvider.java:272)
	at org.nuxeo.ecm.platform.query.nxql.CoreQueryDocumentPageProvider.getCurrentPage(CoreQueryDocumentPageProvider.java:112)
	at org.nuxeo.ecm.automation.core.util.PaginablePageProvider.<init>(PaginablePageProvider.java:41)
	at org.nuxeo.ecm.automation.jaxrs.io.documents.PaginableDocumentModelListImpl.<init>(PaginableDocumentModelListImpl.java:49)
	at org.nuxeo.ecm.automation.core.operations.services.query.DocumentPaginatedQuery.run(DocumentPaginatedQuery.java:149)