Describe the bug
Git ui is not able to push/pull when behind corporate proxy

To Reproduce
Steps to reproduce the behavior:

1. Commit a change
2. Try to push it (press p)
   or
3. open gitui
4. Try to pull ( press f )

Expected behavior
Being able to push commits to remote when running behind porxy

Screenshots
When pulling following message comes up

but when git pull is run from same terminal it works

$ git pull
Already up to date.

Context (please complete the following information):

• PopOS (21.10) [ Ubuntu 21.10 ]
• gitui 0.18.0
• rustc 1.56.1 (59eed8a2a 2021-11-01)

Proxy is set using environment variables http_proxy & https_proxy