publishing fails with bad error report
This error message is not very informative, please write something that help to detect what I actually did wrong.

```
$nimble publish
       Info Hint: used config file '/home/arne/proj/nim/Nim/config/nim.cfg' [Conf]
      Info: Using GitHub API Token in file: /home/arne/.nimble/github_api_token
   Success: Verified as krux02
    Cloning packages into: /tmp/nimble-packages-fork
   Updating the fork
    Prompt: Whitespace separated list of tags?
    Answer: gui rendering opengl
    Pushing to remote of fork.
       Info Creating PR
Error: unhandled exception: Connection was closed before full request has been made [ProtocolError]
```