upload files in a folder
             Parameters
            ==========
            request: the prepared request
            resources: the files to upload
            folder: the folder to upload from
            quiet: suppress verbose output (default is False)

def upload_files(self,
                     request,
                     resources,
                     folder,
                     quiet=False,
                     dir_mode='skip'):
        """ upload files in a folder
             Parameters
            ==========
            request: the prepared request
            resources: the files to upload
            folder: the folder to upload from
            quiet: suppress verbose output (default is False)
        """
        for file_name in os.listdir(folder):
            if (file_name == self.DATASET_METADATA_FILE
                    or file_name == self.OLD_DATASET_METADATA_FILE
                    or file_name == self.KERNEL_METADATA_FILE):
                continue
            full_path = os.path.join(folder, file_name)

            if os.path.isfile(full_path):
                exitcode = self._upload_file(file_name, full_path, quiet,
                                             request, resources)
                if exitcode:
                    return
            elif os.path.isdir(full_path):
                if dir_mode in ['zip', 'tar']:
                    temp_dir = tempfile.mkdtemp()
                    try:
                        _, dir_name = os.path.split(full_path)
                        archive_path = shutil.make_archive(
                            os.path.join(temp_dir, dir_name), dir_mode,
                            full_path)
                        _, archive_name = os.path.split(archive_path)
                        exitcode = self._upload_file(archive_name,
                                                     archive_path, quiet,
                                                     request, resources)
                    finally:
                        shutil.rmtree(temp_dir)
                    if exitcode:
                        return
                elif not quiet:
                    print("Skipping folder: " + file_name +
                          "; use '--dir-mode' to upload folders")
            else:
                if not quiet:
                    print('Skipping: ' + file_name)