function done( error ) {
		if ( errFLG ) {
			return;
		}
		if ( error ) {
			errFLG = true;
			return clbk( error );
		}
		count += 1;
		debug( 'Resolved %d of %d packages.', count, len );
		if ( count === len ) {
			debug( 'Resolved all packages.' );
			return clbk( null, results );
		}
	}
Callback invoked upon resolving dependencies.

@private
@param {(Error|null)} [error] - error object
@returns {void}