Issue #2334383 by jbrown, ashutoshsngh, er.pushpinderrana: Remove usage of form_error().

core/includes/form.inc

core/lib/Drupal/Core/Render/Element/MachineName.php

...odules/ckeditor/src/Plugin/CKEditorPlugin/StylesCombo.php

core/modules/editor/src/Plugin/EditorPluginInterface.php

...e/src/Plugin/entity_reference/selection/SelectionBase.php

core/modules/file/file.module

core/modules/file/src/Plugin/Field/FieldType/FileItem.php

core/modules/image/src/Plugin/Field/FieldType/ImageItem.php

core/modules/rest/src/Plugin/views/row/DataFieldRow.php

.../form_test/src/Form/FormTestLimitValidationErrorsForm.php

...dules/form_test/src/Form/FormTestValidateRequiredForm.php

...les/taxonomy/src/Plugin/views/filter/TaxonomyIndexTid.php

core/modules/user/src/Plugin/views/access/Role.php

core/modules/user/src/Plugin/views/filter/Name.php

.../src/Plugin/entity_reference/selection/ViewsSelection.php

core/modules/views/src/Plugin/views/cache/Time.php

...ules/views/src/Plugin/views/display/DisplayPluginBase.php

core/modules/views/src/Plugin/views/display/Page.php

core/modules/views/src/Plugin/views/field/Serialized.php

core/modules/views/src/Plugin/views/filter/Date.php