Plone 5.08 upgrade to 5.1 Error: Couldn’t find a distribution for ‘Plone==5.1.0’

[mactrash]

This fix my problem

Buildout not working / Couldn't find index page for / Couldn't find a distribution / Disabling non HTTPS access to APIs on PyPI

The easiest fix without updating zc.buildout for more recent zc.buildout and setuptools versions is to create/modify your buildout config or the default.cfg (on unixes in ~/.buildout/default.cfg) and add under the [buildout] section: index = https://pypi.python.org/simple So that https is used for index access.