Allow to pick python version in CI tools

Change-Id: I96c1e26af6aaefa26b164ed9dd9ff0e29fb702af

roles/run-tox/defaults/main.yaml

@@ -1,3 +1,4 @@
 tox_dir: /opt/stack/tobiko
 tox_envlist: scenario
 tox_extra_args: ''
+tox_python_version: ''

roles/run-tox/tasks/main.yaml

@@ -1,6 +1,8 @@
-- name: Run Tobiko
-  command: tools/ci/tox -e {{tox_envlist}} {{tox_extra_args}}
-  args:
-    chdir: "{{tox_dir}}"
+- name: Run Tobiko test cases
+  shell:
+    chdir: "{{ tox_dir }}"
+    cmd: |
+      export PYTHON_VERSION={{ tox_python_version }}
+      tools/ci/tox -e "{{ tox_envlist }}" {{ tox_extra_args }}
   become: true
   become_user: stack

tools/ci/activate

@@ -1,3 +1,8 @@
-CI_TOOLS_DIR=$(dirname "${BASH_SOURCE[0]}")
-CI_TOOLS_DIR=$("${CI_TOOLS_DIR}/realpath" "${CI_TOOLS_DIR}")
-PATH=${CI_TOOLS_DIR}:${PATH}
+function tools_dir {
+    local tools_dir=$(dirname "${BASH_SOURCE[0]}")
+    PATH=${CI_TOOLS_ORIGINAL_PATH:-${PATH}} "${tools_dir}/realpath" "${tools_dir}"
+}
+
+export CI_TOOLS_DIR=${CI_TOOLS_DIR:-$(tools_dir)}
+export CI_TOOLS_ORIGINAL_PATH=${CI_TOOLS_ORIGINAL_PATH:-${PATH}}
+export PATH=${CI_TOOLS_DIR}:${PATH}

tools/ci/python

@@ -0,0 +1,56 @@
+#!/bin/bash
+
+source $(dirname "$0")/activate
+
+PYTHON_VERSION=${PYTHON_VERSION:-}
+
+
+function python() {
+    # call get_python_exe only the first time it is required
+    export PYTHON_EXECUTABLE=${PYTHON_EXECUTABLE:-$(python_executable)}
+    "${PYTHON_EXECUTABLE}" "$@"
+}
+
+
+function python_executable() {
+    local version=${PYTHON_VERSION}
+
+    select_python_executables "${version}" \
+        $(list_python_executables "${version}") | head -1
+}
+
+
+function list_python_executables() {
+    PATH=${CI_TOOLS_ORIGINAL_PATH} which $(list_python_names "${version}")
+}
+
+
+function list_python_names() {
+    local version=${1:-}
+    if [ "${version}" != "" ]; then
+        echo "python${version}"
+    fi
+    echo python3
+    echo python
+}
+
+
+function select_python_executables() {
+    local version=${1:-}
+    local executable
+    shift
+    for executable in "$@"; do
+        "${executable}" -c "${SELECT_PYTHON_EXECUTABLE_SCRIPT}" "${version}"
+    done
+}
+
+
+read -r -d '' SELECT_PYTHON_EXECUTABLE_SCRIPT << END_OF_SCRIPT
+import sys
+version = ".".join(str(i) for i in sys.version_info[:3])
+if version.startswith(sys.argv[1]):
+    print(sys.executable)
+END_OF_SCRIPT
+
+
+python "$@"

tools/ci/tox

@@ -6,7 +6,8 @@ source $(dirname "$0")/activate
 
 
 # Prefer python 3 over python 2
-TOX_BASE_PYTHON=${PYTHON:-$(which python3 || which python)}
+export PYTHON_VERSION=${PYTHON_VERSION:-3}
+TOX_BASE_PYTHON=${PYTHON:-${CI_TOOLS_DIR}/python}
 TOX_VIRTUAL_ENV=$(realpath "${TOX_VIRTUAL_ENV:-.tox/tox}")
 
 
@@ -47,7 +48,7 @@ function tox_setup {
 
 function tox_install_deps {
     if ! "${TOX_BASE_PYTHON}" -m pip --version; then
-        curl https://bootstrap.pypa.io/get-pip.py --user | "${TOX_BASE_PYTHON}"
+        curl https://bootstrap.pypa.io/get-pip.py | "${TOX_BASE_PYTHON}" - --user
     fi
     if ! "${TOX_BASE_PYTHON}" -m virtualenv --version; then
         "${TOX_BASE_PYTHON}" -m pip install --user virtualenv

zuul.d/tobiko-devstack.yaml

@@ -17,6 +17,7 @@
       - x/tobiko
     timeout: 7200
     vars:
+      tox_python_version: 3
       devstack_localrc:
         MULTI_HOST: 0
         USE_PYTHON3: true
@@ -225,6 +226,7 @@
       devstack_localrc:
         # CentOS has no support for Python3
         USE_PYTHON3: false
+      tox_python_version: 2
 
 
 - job: