Issue #2483617 by vasi, phenaproxima: The d6_file migration forgot to mention the uid column

core/modules/migrate_drupal/config/install/migrate.migration.d6_file.yml

@@ -20,5 +20,6 @@ process:
   filesize: filesize
   status: status
   changed: timestamp
+  uid: uid
 destination:
   plugin: entity:file

core/modules/migrate_drupal/src/Tests/d6/MigrateFileTest.php

@@ -68,6 +68,7 @@ public function testFiles() {
     $this->assertIdentical('39325', $file->getSize());
     $this->assertIdentical('public://image-1.png', $file->getFileUri());
     $this->assertIdentical('image/png', $file->getMimeType());
+    $this->assertIdentical("1", $file->getOwnerId());
     // It is pointless to run the second half from MigrateDrupal6Test.
     if (empty($this->standalone)) {
       return;