Issue #2131851 by tim.plunkett: Form errors must be specific to a form and not a global.

core/includes/authorize.inc

core/includes/form.inc

core/includes/install.core.inc

core/lib/Drupal/Core/Field/WidgetBase.php

core/lib/Drupal/Core/Form/FormBuilder.php

core/lib/Drupal/Core/Form/FormBuilderInterface.php

core/lib/Drupal/Core/Form/FormErrorInterface.php

...es/action/lib/Drupal/action/Plugin/Action/EmailAction.php

...s/aggregator/lib/Drupal/aggregator/FeedFormController.php

...gregator/lib/Drupal/aggregator/Form/CategoryAdminForm.php

...les/aggregator/lib/Drupal/aggregator/Form/OpmlFeedAdd.php

core/modules/ban/lib/Drupal/ban/Form/BanAdmin.php

...ock/lib/Drupal/custom_block/CustomBlockFormController.php

core/modules/block/lib/Drupal/block/BlockBase.php

core/modules/block/lib/Drupal/block/BlockFormController.php

core/modules/book/lib/Drupal/book/Form/BookAdminEditForm.php

core/modules/book/lib/Drupal/book/Form/BookSettingsForm.php

...lib/Drupal/ckeditor/Plugin/CKEditorPlugin/StylesCombo.php

core/modules/color/color.module

core/modules/comment/comment.admin.inc