code: function cleanupFiles(workingDir, zipFileName, callback) {
    // Force rm to be quite. Using exec is ok since no large stdout is to
    // be expected.
    var command = "rm -rf " + workingDir + " " + zipFileName;
    exec(command, function(err) {
      if (callback) {
        callback(err);
      }
    });
  }
docs: Delete all temporary files after the import has (successfully
  or not) finished.
  
  @param workingDir The directory where the contents where unzipped
  @param zipFileName The zip archive we imported