Issue #2030925 by echoz: Quote rtl attribute selector.

core/misc/dropbutton/dropbutton.css

core/misc/dropbutton/dropbutton.theme.css

core/misc/print.css

core/misc/vertical-tabs.css

core/modules/book/css/book.theme.css

core/modules/ckeditor/css/ckeditor.admin.css

core/modules/color/css/color.admin.css

core/modules/comment/css/comment.theme.css

core/modules/contextual/css/contextual.theme.css

core/modules/contextual/css/contextual.toolbar.css

core/modules/dblog/css/dblog.module.css

core/modules/entity_reference/css/entity_reference.admin.css

core/modules/field/css/field.module.css

core/modules/field_ui/css/field_ui.admin.css

core/modules/filter/css/filter.admin.css

core/modules/filter/css/filter.caption.css

core/modules/forum/css/forum.module.css

core/modules/help/css/help.module.css

core/modules/image/css/image.theme.css

core/modules/layout/layouts/static/twocol/two-col.css