docker: xrootd base image

[lnielsen]

Create a base image from inveniosoftware/centos7-python with XRootD libraries included.

Usage:

FROM inveniosoftware/centos7-python:3.6-xrootd
# ...

[ntarocco]

@lnielsen I think there is an issue here. We have created an image: inveniosoftware/centos7-python with a tag 3.6, but the 3.6 python version is hardcoded in the image.
I also saw that @fenekku created a python3.7 one, I guess we will have to publish that one too at some point.
Would I would expect probably is to have something like:

• FROM inveniosoftware/centos7-python3.6
• FROM inveniosoftware/centos7-python3.6:xrootd
• FROM inveniosoftware/centos7-python3.7
• FROM inveniosoftware/centos7-python3.7:xroord
  WDYT?

Link: https://hub.docker.com/u/inveniosoftware

[lnielsen]

I'm not the right one to answer. Back in the days, I remember we thought that it was the python version you would want to change, similar to

FROM python:3.8

I think 3.6 was hardcoded because it was not possible to get 3.7 via rpms at that point

[lnielsen]

See https://github.com/inveniosoftware/docker-invenio/blob/master/python3.7/Dockerfile

[diegodelemos]

Regarding the Docker image name, there was a long discussion on GitHub and real-life (see for reference #1 (comment) and #6 (comment)) which ended up in the compromise with we have right now, if we want to change it again I have nothing against.

[ntarocco]

Blocked by: inveniosoftware/invenio-xrootd#23