WP_Ajax_Upgrader_Skin::error( string|WP_Error $errors )

	public function error( $errors ) {
		if ( is_string( $errors ) ) {
			$string = $errors;
			if ( ! empty( $this->upgrader->strings[ $string ] ) ) {
				$string = $this->upgrader->strings[ $string ];
			}

			if ( false !== strpos( $string, '%' ) ) {
				$args = func_get_args();
				$args = array_splice( $args, 1 );
				if ( ! empty( $args ) ) {
					$string = vsprintf( $string, $args );
				}
			}

			// Count existing errors to generate a unique error code.
			$errors_count = count( $this->errors->get_error_codes() );

			$this->errors->add( 'unknown_upgrade_error_' . ( $errors_count + 1 ), $string );
		} elseif ( is_wp_error( $errors ) ) {
			foreach ( $errors->get_error_codes() as $error_code ) {
				$this->errors->add( $error_code, $errors->get_error_message( $error_code ), $errors->get_error_data( $error_code ) );
			}
		}

		$args = func_get_args();
		call_user_func_array( array( $this, 'parent::error' ), $args );
	}