patch 9.0.1999: Vim9: some error messages can be improved

Problem:  Vim9: some error messages can be improved
Solution: Mention the defining class for variable access error message

closes: #13272

Signed-off-by: Christian Brabandt <cb@256bit.org>
Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Co-authored-by: Ernie Rael <errael@raelity.com>
diff --git a/src/vim9expr.c b/src/vim9expr.c
index 05eb524..c15021e 100644
--- a/src/vim9expr.c
+++ b/src/vim9expr.c
@@ -407,8 +407,8 @@
 	{
 	    if (*name == '_' && !inside_class(cctx, cl))
 	    {
-		semsg(_(e_cannot_access_private_variable_str), m->ocm_name,
-							    cl->class_name);
+		emsg_var_cl_define(e_cannot_access_private_variable_str,
+							m->ocm_name, 0, cl);
 		return FAIL;
 	    }
 
@@ -443,8 +443,8 @@
 	    // it is defined.
 	    if (*name == '_' && cctx->ctx_ufunc->uf_class != cl)
 	    {
-		semsg(_(e_cannot_access_private_variable_str), m->ocm_name,
-							    cl->class_name);
+		emsg_var_cl_define(e_cannot_access_private_variable_str,
+							m->ocm_name, 0, cl);
 		return FAIL;
 	    }