Update form_customization.rst

ThomasLandauer · wouterj · commit 50dfc9097da5 · 2020-11-01T00:31:20.000+01:00
diff --git a/form/bootstrap4.rst b/form/bootstrap4.rst
@@ -77,6 +77,8 @@ If you prefer to apply the Bootstrap styles on a form to form basis, include the
         {{ form(form) }}
     {% endblock %}
 
+.. _reference-forms-bootstrap-error-messages:
+
 Error Messages
 --------------
 
diff --git a/form/form_customization.rst b/form/form_customization.rst
@@ -255,6 +255,11 @@ Renders any errors for the given field.
     {# render any "global" errors not associated to any form field #}
     {{ form_errors(form) }}
 
+.. caution::
+
+    In the Bootstrap 4 form theme, ``form_errors()`` is already included
+    in ``form_label()``, see ":ref:`reference-forms-bootstrap-error-messages`"
+
 .. _reference-forms-twig-widget:
 
 form_widget(form_view, variables)
