protected function sanitize_contributors( $users ) {
		foreach ( $users as $i => $name ) {
			// Contributors should be listed by their WordPress.org Login name (Example: 'Joe Bloggs')
			$user = get_user_by( 'login', $name );

			// Or failing that, by their user_nicename field (Example: 'joe-bloggs')
			if ( ! $user ) {
				$user = get_user_by( 'slug', $name );
			}

			// In the event that something invalid is used, we'll ignore it (Example: 'Joe Bloggs (Australian Translation)')
			if ( ! $user ) {
				unset( $users[ $i ] );
				$this->warnings['contributor_ignored'] = true;
				continue;
			}

			// Overwrite whatever the author has specified with the sanitized nicename.
			$users[ $i ] = $user->user_nicename;
		}

		return $users;
	}