Fix: strip HTML tags from multisite user signup validation errors

Co-authored-by: swissspidy <841956+swissspidy@users.noreply.github.com>

Author: Copilot

features/user.feature

@@ -267,6 +267,23 @@ Feature: Manage WordPress users
       Bob Jones
       """
 
+  Scenario: Creating a user with an existing email in multisite shows a clean error message
+    Given a WP multisite install
+
+    When I run `wp user create bobjones bobjones@example.com`
+    Then STDOUT should not be empty
+
+    When I try `wp user create bobjones2 bobjones@example.com`
+    Then STDERR should contain:
+      """
+      This email address is already registered.
+      """
+    And STDERR should not contain:
+      """
+      <
+      """
+    And the return code should be 1
+
   Scenario: Managing user roles
     Given a WP install
 

src/User_Command.php

@@ -460,7 +460,8 @@ public function create( $args, $assoc_args ) {
 		if ( is_multisite() ) {
 			$result = wpmu_validate_user_signup( $user->user_login, $user->user_email );
 			if ( ! empty( $result['errors']->errors ) ) {
-				WP_CLI::error( $result['errors'] );
+				$error_message = implode( ' ', array_map( 'wp_strip_all_tags', $result['errors']->get_error_messages() ) );
+				WP_CLI::error( $error_message );
 			}
 			$user_id = wpmu_create_user( $user->user_login, $user->user_pass, $user->user_email );
 			if ( ! $user_id ) {
@@ -1228,7 +1229,7 @@ public function import_csv( $args, $assoc_args ) {
 				if ( is_multisite() ) {
 					$result = wpmu_validate_user_signup( $new_user['user_login'], $new_user['user_email'] );
 					if ( ! empty( $result['errors']->errors ) ) {
-						WP_CLI::warning( $result['errors'] );
+						WP_CLI::warning( implode( ' ', array_map( 'wp_strip_all_tags', $result['errors']->get_error_messages() ) ) );
 						continue;
 					}
 					$user_id = wpmu_create_user( $new_user['user_login'], $new_user['user_pass'], $new_user['user_email'] );