CentOS install fails with 'python3: command not found'

[Stephen Finucane]

Deploying DevStack master with 'USE_PYTHON3=True' results in the following error:

  /home/centos/devstack/functions-common: line 2309: python3: command not found

CentOS doesn't provide official Python packages so you need to rely on so you need to use packages from centos7.iuscommunity.org [1]. These packages do not seem to provide a python3 symlink. We can either configure this symlink ourselves or, better, call the versioned executable directly.

[1] https://www.digitalocean.com/community/tutorials/how-to-install-python-3-and-set-up-a-local-programming-environment-on-centos-7

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/535365

[Ian Wienand (iwienand)]

This does seem to be "bad" packaging (I'm sure there's some obscure reason) ... so i'm not sure if it turns out we need more extensive work-arounds we'd want that.

I think the more official way to do this on centos is using software collections; although that has it's own range of problems you might be able to source that first and run devstack, in theory at least

[1] https://www.softwarecollections.org/en/scls/rhscl/rh-python35/

[Stephen Finucane (stephenfinucane)]

I agree and I had forgotten about SCL. Thanks for the reminder :) (I might add this to the DevStack Python3 docs shortly).

Agreed that this probably something we shouldn't need extensive workarounds for (e.g. the "configure the symlink" idea), but the proposed solution should hopefully be non-invasive.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/535365
Committed: https://git.openstack.org/cgit/openstack-dev/devstack/commit/?id=ffd0047afa78bfd4d6576afe1d4b8c79435b158c
Submitter: Zuul
Branch: master

commit ffd0047afa78bfd4d6576afe1d4b8c79435b158c
Author: Stephen Finucane <email address hidden>
Date: Thu Jan 18 15:12:29 2018 +0000

    functions-common: Don't reguess Python versions

    We have already established the correct version of Python to use during
    installation, either automatically or through user-provided information
    (USE_PYTHON3, PYTHON3_VERSION). Don't do it again.

    Change-Id: I7bdf2be9a885994bf2c437dd104048a1ff2f6666
    Closes-Bug: #1744096