function onPath( error, path ) {
		if ( error ) {
			return clbk( error );
		}
		if ( path === null ) {
			error = new Error( 'unexpected error. Unable to resolve package directory as unable to find a \'package.json\' in a parent directory.' );
			return clbk( error );
		}
		clbk( null, dirname( path ) );
	}
Callback invoked upon resolving a `package.json`.

@private
@param {(Error|null)} error - error object
@param {(string|null)} path - path or null
@returns {void}