After failing with pip and easy_install I came across this post again: https://forum.zato.io/t/what-is-the-canonical-way-to-add-extra-python-packages-to-my-zato-server/580?source_topic_id=586 There is another way, that of updating versions.cfg and buildout.cfg files but if you are more familiar with pip than buildout then pip install package-name is perfectly fine. So it turns out it is as easy as: nano ~/current/versions.cfgupdate the version from … Continue reading Upgrading requests_toolbelt in Zato 2.0.8