I finally figured out what happened with assistance from circleCI team.
The problem relates to the HTTP_PROXY environment , but as a side effect,
I am not using HTTP_PROXY for heroku cli but as an parameter to inject into my heroku container,
it turns out I can not use the HTTP_PROXY as a name for that environment variable since the heroku cli picks it up and attempts to use it
(I did not realise that since I am not using a firewall at work)
Basically I need to use MY_HTTP_PROXY as a name for the environment variable