Closes #171

Proposed Changes

According to specification of Flux, the error could be propagated after "success" table:

When an error occurs after some results have already been sent to the client the error will be encoded as the next table and the rest of the results will be discarded. In such a case the HTTP status code cannot be changed and will remain as 200 OK.

https://github.com/influxdata/flux/blob/master/docs/SPEC.md#errors

Checklist

• CHANGELOG.md updated
• Rebased/mergeable
• A test has been added if appropriate
• mvn test completes successfully
• Commit messages are in semantic format
• Sign CLA (if not already signed)