Multisite: Improve wording when creating a user with a reserved email address.

This updates the user-facing message displayed when attempting to create a user with an email address that is already pending activation in a multisite network.

Props realloc, valendesigns, jeremyfelt, SirLouen, westonruter, trepmal, johnbillion, BurlesonBrad, garrett-eclipse, spacedmonkey, westonruter.
Fixes #30227.


git-svn-id: https://develop.svn.wordpress.org/trunk@61074 602fd350-edb4-49c9-b593-d223f7449a82

Author: westonruter

src/wp-includes/ms-functions.php

@@ -570,7 +570,7 @@ function wpmu_validate_user_signup( $user_name, $user_email ) {
 		if ( $diff > 2 * DAY_IN_SECONDS ) {
 			$wpdb->delete( $wpdb->signups, array( 'user_email' => $user_email ) );
 		} else {
-			$errors->add( 'user_email', __( 'That email address has already been used. Please check your inbox for an activation email. It will become available in a couple of days if you do nothing.' ) );
+			$errors->add( 'user_email', __( 'That email address is pending activation and is not available for new registration. If you made a previous attempt with this email address, please check your inbox for an activation email. If left unconfirmed, it will become available in a couple of days.' ) );
 		}
 	}