function onExists( error, bool ) { // eslint-disable-line handle-callback-err
		if ( bool ) {
			return done( null, spath );
		}
		// Resolve a parent directory:
		child = dir;
		dir = resolve( dir, '..' );

		// If we have already reached root, we cannot resolve any higher directories...
		if ( child === dir ) {
			return done( null, null );
		}
		// Resolve the next search path:
		spath = resolve( dir, path );
		exists( spath, onExists );
	}
Callback invoked after checking for path existence.

@private
@param {(Error|null)} error - error object
@param {boolean} bool - boolean indicating if a path exists
@returns {void}