feat(python): check code formatting using `black`

templates/Python.yaml

+# -*- coding: utf-8 -*-
+# vim: ft=yaml
+#
+# Hidden template jobs to be used in `.gitlab-ci.yml`
+#
+# - `.python:black:check`: verify formatting of code with `black`
+#
+---
+#
+# .python:black:check
+# ===================
+#
+# The Python code must match `black` standard.
+#
+# USAGE
+# =====
+#
+# include:
+#   - project: EOLE/Infra/ci-tools
+#     ref: stable
+#     file: /templates/Python.yaml
+#
+# stages:
+#   - lint
+#
+# python:black: {extends: '.python:black:check'}
+#
+# REQUIREMENTS
+# ============
+#
+# - a `lint` stage must be present in your pipeline or it must be
+#   overriden by the extending job to feet your need
+#
+# - the `.not-on-stable` rules templates
+#
+# OPTIONAL VARIABLES
+# ==================
+#
+# - `PYTHON_BLACK_OPTS`: additional options to pass to `black`
+#
+# - `PYTHON_SOURCE_DIR`: top level directory where to run `black`,
+#   defaults to `.`
+#
+# - `PYTHON_BLACK_IMAGE`: name of the black docker image to use
+#
+.python:black:check:
+  stage: lint
+  extends: .not-on-stable
+  image: "${PYTHON_BLACK_IMAGE}"
+  variables:
+    PYTHON_BLACK_IMAGE: "hub.eole.education/proxyhub/pyfound/black:latest_release"
+    PYTHON_BLACK_OPTS: ''
+    PYTHON_SOURCE_DIR: '.'
+  script:
+    - echo -e "\e[0Ksection_start:`date +%s`:python-black\r\e[0KExecute 'black --check ${PYTHON_BLACK_OPTS} ${PYTHON_SOURCE_DIR}'"
+    - black --check ${PYTHON_BLACK_OPTS} ${PYTHON_SOURCE_DIR}
+    - echo -e "\e[0Ksection_end:`date +%s`:python-black\r\e[0K"
+...