Looks like the constraints needs to be updated or overridden to allow plone.volto installation with python 3.9
$ mkdir Plone-5
$ python -m venv .
$ source bin/activate
$ echo '[buildout]
parts = instance
extends =
https://dist.plone.org/release/5.2-latest/versions.cfg
#versions = versions
[instance]
recipe = plone.recipe.zope2instance
eggs =
Plone
plone.volto
' > buildout.cfg
$ ./bin/pip install -r https://dist.plone.org/release/5.2-latest/requirements.txt
Running './bin/buildout -vvv' resulting in following constraint error:
We have the distribution that satisfies 'Zope==4.6.3'.
Getting required 'ZODB==5.6.0'
We have the distribution that satisfies 'ZODB==5.6.0'.
Getting required 'ZEO==5.2.2'
We have the distribution that satisfies 'ZEO==5.2.2'.
Getting required 'Paste==3.5.0'
We have the distribution that satisfies 'Paste==3.5.0'.
Version and requirements information containing plone.restapi:
[versions] constraint on plone.restapi: 7.5.0
Requirement of plone.volto: plone.restapi>=8.13.0
Requirement of Plone==5.2.6: plone.restapi
While:
Installing instance.
Error: The requirement ('plone.restapi>=8.13.0') is not allowed by your [versions] constraint (7.5.0)