Improve error handling for 400

[dzmitry-lahoda]

I get next error:

HTTP/1.1 400 Bad Request
Server: nginx/1.12.2
Date: Fri, 22 May 2020 17:12:34 GMT
Content-Type: application/json
Content-Length: 99
Connection: keep-alive

{"statement_id":0,"error":"query not allowed: accessing database \"foobarbaz\" is not allowed"}

And see:

Expected:

If you cannot parse resonces, at least provide it error code and inner text

[mvadu]

I will work on it.