When executing:

```
s3AsyncClient.headBucket(HeadBucketRequest.builder()
                    .bucket("local-stack-test-bucket")
                    .build()).join();
```

We get this exception thrown (Java): java.util.concurrent.CompletionException: software.amazon.awssdk.services.s3.model.S3Exception: null (Service: S3, Status Code: 502, Request ID: null)

I narrowed this down to db4cddea4e4844c1241cca5ac22ecbde08e52064 and found the problem. PR incoming shortly.
self.request = request
        self.client_address = client_address
        self.server = server
        self.proxy = server.my_object
        self.data_bytes = None
        self.protocol_version = self.proxy.protocol_version
        try:
            BaseHTTPRequestHandler.__init__(self, request, client_address, server)
        except SSLError as e:
            LOG.warning('SSL error when handling request: %s' % e)
    def parse_request(self):
        result = BaseHTTPRequestHandler.parse_request(self)
        if not result:
            return result
        if sys.version_info[0] >= 3:
            return result
        
        
        expect = self.headers.get('Expect', '')
        if (expect.lower() == '100-continue' and
                self.protocol_version >= 'HTTP/1.1' and
                self.request_version >= 'HTTP/1.1'):
            if self.request_version != 'HTTP/0.9':
                self.wfile.write(('%s %d %s\r\n' %
                    (self.protocol_version, 100, 'Continue')).encode('latin1', 'strict'))
                self.end_headers()
        return result
    def do_GET(self):