Deletes the file_lists cache files

def clear_file_list_cache(self, load):
        '''
        Deletes the file_lists cache files
        '''
        if 'env' in load:
            # "env" is not supported; Use "saltenv".
            load.pop('env')

        saltenv = load.get('saltenv', [])
        if saltenv is not None:
            if not isinstance(saltenv, list):
                try:
                    saltenv = [x.strip() for x in saltenv.split(',')]
                except AttributeError:
                    saltenv = [x.strip() for x in six.text_type(saltenv).split(',')]

            for idx, val in enumerate(saltenv):
                if not isinstance(val, six.string_types):
                    saltenv[idx] = six.text_type(val)

        ret = {}
        fsb = self.backends(load.pop('fsbackend', None))
        list_cachedir = os.path.join(self.opts['cachedir'], 'file_lists')
        try:
            file_list_backends = os.listdir(list_cachedir)
        except OSError as exc:
            if exc.errno == errno.ENOENT:
                log.debug('No file list caches found')
                return {}
            else:
                log.error(
                    'Failed to get list of saltenvs for which the master has '
                    'cached file lists: %s', exc
                )

        for back in file_list_backends:
            # Account for the fact that the file_list cache directory for gitfs
            # is 'git', hgfs is 'hg', etc.
            back_virtualname = re.sub('fs$', '', back)
            try:
                cache_files = os.listdir(os.path.join(list_cachedir, back))
            except OSError as exc:
                log.error(
                    'Failed to find file list caches for saltenv \'%s\': %s',
                    back, exc
                )
                continue
            for cache_file in cache_files:
                try:
                    cache_saltenv, extension = cache_file.rsplit('.', 1)
                except ValueError:
                    # Filename has no dot in it. Not a cache file, ignore.
                    continue
                if extension != 'p':
                    # Filename does not end in ".p". Not a cache file, ignore.
                    continue
                elif back_virtualname not in fsb or \
                        (saltenv is not None and cache_saltenv not in saltenv):
                    log.debug(
                        'Skipping %s file list cache for saltenv \'%s\'',
                        back, cache_saltenv
                    )
                    continue
                try:
                    os.remove(os.path.join(list_cachedir, back, cache_file))
                except OSError as exc:
                    if exc.errno != errno.ENOENT:
                        log.error('Failed to remove %s: %s',
                                  exc.filename, exc.strerror)
                else:
                    ret.setdefault(back, []).append(cache_saltenv)
                    log.debug(
                        'Removed %s file list cache for saltenv \'%s\'',
                        cache_saltenv, back
                    )
        return ret