code: function clearPriorOutput(directory, sourceImageBasename) {
    const ext = path.extname(sourceImageBasename);
    const extlessBasename = path.basename(sourceImageBasename, ext);
    return del(path.join(directory, `${extlessBasename}*.*`));
  }
docs: Delete all prior generated versions of an image source file.
  
  @param {string} directory
  @param {string} sourceImageBasename
  @return {Promise<void>} - Resolves when the versions are deleted.