Update to Drupal 8.0.0-beta15. For more information, see: https://www.drupal.org/node/2563023

core/modules/user/src/UserServiceProvider.php

@@ -0,0 +1,30 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\user\UserServiceProvider.
+ */
+
+namespace Drupal\user;
+
+use Drupal\Core\DependencyInjection\ServiceModifierInterface;
+use Drupal\Core\DependencyInjection\ContainerBuilder;
+
+/**
+ * Swaps the original 'password' service in order to handle password hashing for
+ * user migrations that have passwords hashed to MD5.
+ *
+ * @see \Drupal\migrate\MigratePassword
+ * @see \Drupal\Core\Password\PhpassHashedPassword
+ */
+class UserServiceProvider implements ServiceModifierInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function alter(ContainerBuilder $container) {
+    $container->setDefinition('password_original', $container->getDefinition('password'));
+    $container->setDefinition('password', $container->getDefinition('password_migrate'));
+  }
+
+}