Make pub publish more user friendly:

utils/pub/validator/license.dart

Index: utils/pub/validator/license.dart
diff --git a/utils/pub/validator/license.dart b/utils/pub/validator/license.dart
index 46a1c4087669fb179451ea76b70112d5184361ff..fcc6a49c2f273b12ef12f90fa18217ea61c987bc 100644
--- a/utils/pub/validator/license.dart
+++ b/utils/pub/validator/license.dart
@@ -20,9 +20,10 @@ class LicenseValidator extends Validator {
           r"^([a-zA-Z0-9]+[-_])?(LICENSE|COPYING)(\..*)?$");
       if (files.map(basename).some(licenseLike.hasMatch)) return;
 
-      errors.add("Your package must have a COPYING or LICENSE file containing "
-          "an open-source license. For more details, see "
-          "http://pub.dartlang.org/doc/pub-lish.html.");
+      errors.add(
+          "You must have a COPYING or LICENSE file in the root directory.\n"
+          "An open-source license helps ensure people can legally use your "
+          "code.");
     });
   }
 }