git pull origin pull/939/head

git checkout -b remove-python-support

<make changes>

git commit
git push origin remove-python-support
git checkout master
git remote add upstream https://github.com/xxx/...
git fetch upstream
git rebase upstream/master

this way, if you have any uncommited changes in a feature branch, git will stop you you could commit them, or stash them also after, it's easier to rebase on clean master