patch 9.0.1926: Vim9: not enough info in error message

Problem:  Vim9: not enough info in error message
Solution: Add class name, change member to variable, quote names

closes: #13136

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Ernie Rael <errael@raelity.com>
diff --git a/src/errors.h b/src/errors.h
index f1373a4..40e16f1 100644
--- a/src/errors.h
+++ b/src/errors.h
@@ -3411,7 +3411,7 @@
 	INIT(= N_("E1333: Cannot access private member: %s"));
 // E1334 unused
 EXTERN char e_member_is_not_writable_str[]
-	INIT(= N_("E1335: Member is not writable: %s"));
+	INIT(= N_("E1335: Variable \"%s\" in class \"%s\" is not writable"));
 #endif
 EXTERN char e_internal_error_shortmess_too_long[]
 	INIT(= "E1336: Internal error: shortmess too long");