Update to Drupal 8.1.2. For more information, see https://www.drupal.org/project/drupal/releases/8.1.2

core/lib/Drupal/Core/Plugin/Context/ContextHandlerInterface.php

@@ -17,7 +17,7 @@ interface ContextHandlerInterface {
    *
    * @param \Drupal\Component\Plugin\Context\ContextInterface[] $contexts
    *   An array of contexts.
-   * @param array $definitions .
+   * @param array $definitions
    *   An array of plugin definitions.
    *
    * @return array

core/lib/Drupal/Core/Plugin/DefaultSingleLazyPluginCollection.php

@@ -82,11 +82,11 @@ class DefaultSingleLazyPluginCollection extends LazyPluginCollection {
    * {@inheritdoc}
    */
   public function setConfiguration($configuration) {
+    $this->configuration = $configuration;
     $plugin = $this->get($this->instanceId);
     if ($plugin instanceof ConfigurablePluginInterface) {
       $plugin->setConfiguration($configuration);
     }
-    $this->configuration = $configuration;
     return $this;
   }
 
@@ -94,6 +94,7 @@ class DefaultSingleLazyPluginCollection extends LazyPluginCollection {
    * {@inheritdoc}
    */
   public function addInstanceId($id, $configuration = NULL) {
+    $this->instanceId = $id;
     parent::addInstanceId($id, $configuration);
     if ($configuration !== NULL) {
       $this->setConfiguration($configuration);

core/lib/Drupal/Core/Plugin/Discovery/HookDiscovery.php

@@ -55,4 +55,5 @@ class HookDiscovery implements DiscoveryInterface {
     }
     return $definitions;
   }
+
 }

core/lib/Drupal/Core/Plugin/Discovery/YamlDiscovery.php

@@ -101,4 +101,5 @@ class YamlDiscovery implements DiscoveryInterface {
 
     return $definitions;
   }
+
 }