--- scheduler.cron.inc.16	2016-02-08 13:42:13.000000000 +0000
+++ scheduler.cron.inc	2016-02-08 13:47:14.000000000 +0000
@@ -12,6 +12,12 @@
 use Drupal\node\Entity\Node;
 
 /**
+ * Declare exception classes.
+ */
+class SchedulerNodeTypeNotEnabledException extends Exception {}
+class SchedulerMissingDateException extends Exception {}
+
+/**
  * Publish scheduled nodes.
  *
  * @return bool
@@ -25,6 +31,8 @@
   $query = \Drupal::entityQuery('node')
     ->condition('publish_on', 0, '>')
     ->condition('publish_on', REQUEST_TIME, '<=');
+  // @todo Change this query to exclude nodes which are not enabled for
+  // publishing. See https://www.drupal.org/node/2659824
   $nids = $query->execute();
 
   $action = 'publish';
@@ -36,22 +44,14 @@
   \Drupal::moduleHandler()->alter('scheduler_nid_list', $nids, $action);
 
   $logger = \Drupal::logger('scheduler');
+  // @todo Use dependency injection for the logger when we have written the new
+  // service for scheduler API. See https://www.drupal.org/node/2651338
   $nodes = Node::loadMultiple($nids);
   foreach ($nodes as $nid => $node) {
-    $view_link = $node->link(t('View node'));
-    $nodetype_url = Url::fromRoute('entity.node_type.edit_form', array('node_type' => $node->getType()));
-    $nodetype_link = \Drupal::l(t('Settings'), $nodetype_url);
-    $logger_variables = array(
-      '@type' => $node->getType(),
-      '%title' => $node->getTitle(),
-      '%field' => $node->publish_on->label, // @todo this does not work. How to get the label text?
-      'link' => $nodetype_link . ' ' . $view_link,
-    );
-
-    // The above query and api calls can return nodes of types which are not
-    // enabled for this scheduler action. Do not process these.
+    // The API calls could return nodes of types which are not enabled for
+    // scheduled publishing. Do not process these.
     if (!$node->type->entity->getThirdPartySetting('scheduler', $action . '_enable', FALSE)) {
-      $logger->warning('"%title" not published because @type node type is not enabled for Scheduler', $logger_variables);
+      throw new SchedulerNodeTypeNotEnabledException(sprintf("Node %d '%s' will not be published because node type '%s' is not enabled for scheduled unpublishing", $node->id(), $node->getTitle(), node_get_type_label($node)));
       continue;
     }
 
@@ -64,10 +64,12 @@
     // @todo For D8 move the 'pre' call to here.
     // See https://www.drupal.org/node/2311273
 
-    // Ensure we have a valid date to avoid a cron crash if third-party modules
-    // have altered the node list or node data via the API calls above.
+    // If an API call has removed the date $node->set('changed', $publish_on)
+    // would fail, so trap this exception here and give a meaningful message.
     if (empty($node->publish_on->value)) {
-      $logger->error('@type "%title" not published because %field field has no value', $logger_variables);
+      $field_definitions = \Drupal::entityManager()->getFieldDefinitions('node', $node->getType());
+      $field = (string)$field_definitions['publish_on']->getLabel();
+      throw new SchedulerMissingDateException(sprintf("Node %d '%s' will not be published because field '%s' has no value", $node->id(), $node->getTitle(), $field));
       continue;
     }
 
@@ -98,6 +100,14 @@
     _scheduler_scheduler_api($node, 'pre_' . $action);
 
     // Log the fact that a scheduled publication is about to take place.
+    $view_link = $node->link(t('View node'));
+    $nodetype_url = Url::fromRoute('entity.node_type.edit_form', array('node_type' => $node->getType()));
+    $nodetype_link = \Drupal::l(node_get_type_label($node) . ' ' . t('settings'), $nodetype_url);
+    $logger_variables = array(
+      '@type' => node_get_type_label($node),
+      '%title' => $node->getTitle(),
+      'link' => $nodetype_link . ' ' . $view_link,
+    );
     $logger->notice('@type: scheduled publishing of %title.', $logger_variables);
 
     // Use the actions system to publish the node.
@@ -131,6 +141,8 @@
   $query = \Drupal::entityQuery('node')
     ->condition('unpublish_on', 0, '>')
     ->condition('unpublish_on', REQUEST_TIME, '<=');
+  // @todo Change this query to exclude nodes which are not enabled for
+  // unpublishing. See https://www.drupal.org/node/2659824
   $nids = $query->execute();
 
   $action = 'unpublish';
@@ -142,22 +154,14 @@
   \Drupal::moduleHandler()->alter('scheduler_nid_list', $nids, $action);
 
   $logger = \Drupal::logger('scheduler');
+  // @todo Use dependency injection for the logger when we have written the new
+  // service for scheduler API. See https://www.drupal.org/node/2651338
   $nodes = Node::loadMultiple($nids);
   foreach ($nodes as $nid => $node) {
-    $view_link = $node->link(t('View node'));
-    $nodetype_url = Url::fromRoute('entity.node_type.edit_form', array('node_type' => $node->getType()));
-    $nodetype_link = \Drupal::l(t('Settings'), $nodetype_url);
-    $logger_variables = array(
-      '@type' => $node->getType(),
-      '%title' => $node->getTitle(),
-      '%field' => $node->unpublish_on->label,
-      'link' => $nodetype_link . ' ' . $view_link,
-    );
-
-    // The above query and api calls can return nodes of types which are not
-    // enabled for this scheduler action. Do not process these.
+    // The API calls could return nodes of types which are not enabled for
+    // scheduled unpublishing. Do not process these.
     if (!$node->type->entity->getThirdPartySetting('scheduler', $action . '_enable', FALSE)) {
-      $logger->warning('"%title" not unpublished because @type node type is not enabled for Scheduler', $logger_variables);
+      throw new SchedulerNodeTypeNotEnabledException(sprintf("Node %d '%s' will not be unpublished because node type '%s' is not enabled for scheduled unpublishing", $node->id(), $node->getTitle(), node_get_type_label($node)));
       continue;
     }
 
@@ -178,10 +182,12 @@
     // @todo For D8, move the 'pre' call to here.
     // See https://www.drupal.org/node/2311273
 
-    // Ensure we have a valid date to avoid cron crash if third-party modules
-    // have altered the node list or node data via the API calls above.
+    // If an API call has removed the date $node->set('changed', $unpublish_on)
+    // would fail, so trap this exception here and give a meaningful message.
     if (empty($node->unpublish_on->value)) {
-      $logger->error('@type "%title" not unpublished because %field field has no value', $logger_variables);
+      $field_definitions = \Drupal::entityManager()->getFieldDefinitions('node', $node->getType());
+      $field = (string)$field_definitions['unpublish_on']->getLabel();
+      throw new SchedulerMissingDateException(sprintf("Node %d '%s' will not be unpublished because field '%s' has no value", $node->id(), $node->getTitle(), $field));
       continue;
     }
 
@@ -209,6 +215,14 @@
     _scheduler_scheduler_api($node, 'pre_' . $action);
 
     // Log the fact that a scheduled unpublication is about to take place.
+    $view_link = $node->link(t('View node'));
+    $nodetype_url = Url::fromRoute('entity.node_type.edit_form', array('node_type' => $node->getType()));
+    $nodetype_link = \Drupal::l(node_get_type_label($node) . ' ' . t('settings'), $nodetype_url);
+    $logger_variables = array(
+      '@type' => node_get_type_label($node),
+      '%title' => $node->getTitle(),
+      'link' => $nodetype_link . ' ' . $view_link,
+    );
     $logger->notice('@type: scheduled unpublishing of %title.', $logger_variables);
 
     // Use the actions system to publish the node.