This happens because a proxy is configured in git.

Since it’s https proxy (and not http) git config http.proxy and git config --global http.proxy can’t help.

1 : take a look at your git configuration

git config --global -l

If you have nothing related to https proxy like https_proxy=... the problem is not here.

If you have something related to https proxy then remove it from the file ~/.gitconfig and try again

2 : if it still doesn’t work, unset environment variables

Check your environment variables :

env|grep -i proxy

You should have one or several lines with https_proxy=...

Unset one by one with :
unset https_proxy (or HTTPS_PROXY depending of the name of the variable)

env|grep -i proxy

If it shows nothing you should be good.

Note : This solution can applies to http and https proxy problems. just the variables name changes from https to http