In [this PR](https://github.com/localstack/localstack/pull/1200/files) we introduced a new way of starting S3 in a separate process.

In the meantime, the service startup has been significantly reworked, and it seems that we can integrate the S3 starter into the [`multiserver.py`](https://github.com/localstack/localstack/blob/master/localstack/utils/server/multiserver.py) based loading approach that loads multiple APIs in a single process, for performance reasons. We should look into that.
bucket_name = 'test-bucket-%s' % short_uid()
        self.s3_client.create_bucket(Bucket=bucket_name)
        
        object_key = 'key-by-hostname'
        url = self.s3_client.generate_presigned_url(
            'put_object', Params={'Bucket': bucket_name, 'Key': object_key})
        
        
        url += '&x-amz-meta-foo=bar'
        
        response = requests.put(url, data='content 123', verify=False)
        self.assertLess(response.status_code, 400)
        
        self.assertEqual('', to_str(response.content))
        response = self.s3_client.head_object(Bucket=bucket_name, Key=object_key)
        self.assertEquals('bar', response.get('Metadata', {}).get('foo'))
        
        self._delete_bucket(bucket_name, [object_key])
    def test_s3_put_metadata_underscores(self):