def delete_all(self):
        for status, keys in six.iteritems(self.list_keys()):
            for key in keys:
                try:
                    os.remove(os.path.join(self.opts['pki_dir'], status, key))
                    eload = {'result': True,
                             'act': 'delete',
                             'id': key}
                    self.event.fire_event(eload, tagify(prefix='key'))
                except (OSError, IOError):
                    pass
        self.check_minion_cache()
        if self.opts.get('rotate_aes_key'):
            salt.crypt.dropfile(self.opts['cachedir'], self.opts['user'])
        return self.list_keys()
Replaces all empty str or unicode values with None and returns the
dataset/ETHPy150Open saltstack/salt/salt/key.py/Key.delete_all--crossover with--dataset/ETHPy150Open ExCiteS/geokey/geokey/contributions/serializers.py/ContributionSerializer.replace_null