fix: raise better error if field widget serialization fails

and log a warning with traceback while we're at it

tests/forms/test_base.py

@@ -587,6 +587,14 @@ class TestForm(WebTestCase):
             html = form.render_vue_field("foo")
             self.assertIn("something is wrong", html)
 
+        class BadWidget(deform.widget.Widget):
+            def serialize(self, **kwargs):
+                raise NotImplementedError
+
+        # widget serialization error
+        dform["foo"].widget = BadWidget()
+        self.assertRaises(RuntimeError, form.render_vue_field, "foo")
+
         # add another field, but not to deform, so it should still
         # display but with no widget
         form.fields.append("zanzibar")