[LNT] Pin Python version in Dockerfile to 3.7 temporarily

[tnfchris]

Summary

Hi All,

Python 3.9 has been released and one of the dependencies of LNT does not compiler under it. pyyaml seems to fail during building:

ext/_yaml.c: In function '__Pyx_modinit_type_init_code':
   ext/_yaml.c:25698:25: error: 'PyTypeObject' {aka 'struct _typeobject'} has no member named 'tp_print'
   25698 |   __pyx_type_5_yaml_Mark.tp_print = 0;
         |                         ^
   ext/_yaml.c:25718:28: error: 'PyTypeObject' {aka 'struct _typeobject'} has no member named 'tp_print'
   25718 |   __pyx_type_5_yaml_CParser.tp_print = 0;
         |                            ^
   ext/_yaml.c:25732:29: error: 'PyTypeObject' {aka 'struct _typeobject'} has no member named 'tp_print'
   25732 |   __pyx_type_5_yaml_CEmitter.tp_print = 0;
         |                             ^

Presumably because the header has changed under python 3.9. For now let's pin the Dockerfile to 3.7 until this is sorted so LNT can still run.

OK for master?

Thanks,
Tamar

[thopre]

Not the first time this happen. I wonder if we should keep the pin on. Sadly docker version don't seem to be real version so there's no way to requires a version "lesser than X"

[tnfchris]

was landed in 60343998f7907b77e24f01c94c48ea6c753eca7e

docker/Dockerfile

-FROM python:alpine
+FROM python:3.7-alpine
 
 RUN apk update \
   && apk add --no-cache --virtual .build-deps git g++ postgresql-dev yaml-dev \