Method standardizeError

src/backend/MountableFileSystem.ts:187–194

* Fixes up error messages so they mention the mounted file location relative * to the MFS root, not to the particular FS's root. * Mutates the input error, and returns it.

(err: ApiError, path: string, realPath: string)

   * Mutates the input error, and returns it.
   */
  public standardizeError(err: ApiError, path: string, realPath: string): ApiError {
    const index = err.message.indexOf(path);
    if (index !== -1) {
      err.message = err.message.substr(0, index) + realPath + err.message.substr(index + path.length);
      err.path = realPath;
    }
    return err;
  }

  // The following methods involve multiple file systems, and thus have custom
  // logic.