Index: wp-includes/class-wp-customize-manager.php
===================================================================
--- wp-includes/class-wp-customize-manager.php	(revision 39543)
+++ wp-includes/class-wp-customize-manager.php	(working copy)
@@ -1561,7 +1561,7 @@
 		 * that the user's session has expired and they need to re-authenticate.
 		 */
 		if ( $this->messenger_channel && ! current_user_can( 'customize' ) ) {
-			$this->wp_die( -1, __( 'Unauthorized. You may remove the customize_messenger_channel param to preview as frontend.' ) );
+			$this->wp_die( -1, __( 'Sorry, you are not allowed to remove the customize_messenger_channel param to preview as frontend.' ) );
 			return;
 		}
 
@@ -1986,7 +1986,7 @@
 				continue;
 			}
 			if ( $options['validate_capability'] && ! current_user_can( $setting->capability ) ) {
-				$validity = new WP_Error( 'unauthorized', __( 'Unauthorized to modify setting due to capability.' ) );
+				$validity = new WP_Error( 'unauthorized', __( 'Sorry, you are not allowed to modify setting.' ) );
 			} else {
 				if ( is_null( $unsanitized_value ) ) {
 					continue;