Source

File: wp-includes/class-wp-recovery-mode.php

public function handle_error( array $error ) {

		$extension = $this->get_extension_for_error( $error );

		if ( ! $extension || $this->is_network_plugin( $extension ) ) {
			return new WP_Error( 'invalid_source', __( 'Error not caused by a plugin or theme.' ) );
		}

		if ( ! $this->is_active() ) {
			if ( ! is_protected_endpoint() ) {
				return new WP_Error( 'non_protected_endpoint', __( 'Error occurred on a non-protected endpoint.' ) );
			}

			if ( ! function_exists( 'wp_generate_password' ) ) {
				require_once ABSPATH . WPINC . '/pluggable.php';
			}

			return $this->email_service->maybe_send_recovery_mode_email( $this->get_email_rate_limit(), $error, $extension );
		}

		if ( ! $this->store_error( $error ) ) {
			return new WP_Error( 'storage_error', __( 'Failed to store the error.' ) );
		}

		if ( headers_sent() ) {
			return true;
		}

		$this->redirect_protected();
	}