Merge pull request #1472 from yliaog/master

replaced 2.7.12 with 3.9.1 version, as python 2 has come to end of life

Author: k8s-ci-robot

devel/release.md

@@ -140,7 +140,7 @@ this step and go back to the master branch if there are any API changes.
 ## Make distribution packages
 
 First make sure you are using a clean version of python. Use virtualenv and
-pyenv packages. Make sure you are using python 2.7.12. I would normally do this
+pyenv packages. Make sure you are using python 3.9.1. I would normally do this
 on a clean machine:
 
 (install [pyenv](https://github.com/yyuu/pyenv#installation))
@@ -149,11 +149,11 @@ on a clean machine:
 
 ```bash
 git clean -xdf
-pyenv install -s 2.7.12
-pyenv global 2.7.12
+pyenv install -s 3.9.1
+pyenv global 3.9.1
 virtualenv .release
 source .release/bin/activate
-python --version     # Make sure you get Python 2.7.12
+python --version     # Make sure you get Python 3.9.1
 pip install twine
 ```