As explained in that thread, your network setup is most likely culprint for the issue - 0 chance that this has anything to do with robot framework.
One option, which i already mentioned is (install manually and modify the url in setup.py to something that your proxy can access):
- download the release.
- unpack the source release to a directory
- fix the issues in setup.py
Worth checking is http_proxy and https_proxy environment variables …