constructor(realPath, cache) {
    this.realPath = realPath;
    this.hasEntries = false; // for speed
    this.entries = Object.create(null);
    this.errors = new ErrorList();
    this.cache = cache;
  }
Class that stores information about a node_modules directory (i.e., the
packages and subdirectories in the directory). It is one of the
two types of entries in a PackageInfoCache. It is only created by the
PackageInfoCache.

@public
@class NodeModulesList