Set default value for PYTHON_VERSION and always set python interpreter

.azure-pipelines/templates/jobs/extended-tests-jobs.yml

@@ -3,6 +3,8 @@ jobs:
     variables:
       - name: IMAGE_NAME
         value: ubuntu-18.04
+      - name: PYTHON_VERSION
+        value: 3.8
       - group: certbot-common
     strategy:
       matrix:

.azure-pipelines/templates/jobs/packaging-jobs.yml

@@ -80,6 +80,7 @@ jobs:
         displayName: Retrieve Windows installer
       - script: |
           py -3 -m venv venv
+          venv\Scripts\python letsencrypt-auto-source\pieces\pipstrap.py
           venv\Scripts\python tools\pip_install.py -e certbot-ci
         displayName: Prepare Certbot-CI
       - script: |
@@ -138,7 +139,9 @@ jobs:
       - script: |
           sudo apt-get update
           sudo apt-get install -y --no-install-recommends nginx-light snapd
-          python tools/pip_install.py -U tox
+          python3 -m venv venv
+          venv/bin/python letsencrypt-auto-source/pieces/pipstrap.py
+          venv/bin/python tools/pip_install.py -U tox
         displayName: Install dependencies
       - task: DownloadPipelineArtifact@2
         inputs:
@@ -149,7 +152,7 @@ jobs:
           sudo snap install --dangerous --classic snap/certbot_*_amd64.snap
         displayName: Install Certbot snap
       - script: |
-          python -m tox -e integration-external,apacheconftest-external-with-pebble
+          venv/bin/python -m tox -e integration-external,apacheconftest-external-with-pebble
         displayName: Run tox
   - job: snap_dns_run
     dependsOn: snaps_build
@@ -171,6 +174,7 @@ jobs:
         displayName: Retrieve Certbot snaps
       - script: |
           python3 -m venv venv
+          venv/bin/python letsencrypt-auto-source/pieces/pipstrap.py
           venv/bin/python tools/pip_install.py -e certbot-ci
         displayName: Prepare Certbot-CI
       - script: |

.azure-pipelines/templates/jobs/standard-tests-jobs.yml

@@ -1,5 +1,7 @@
 jobs:
   - job: test
+    variables:
+      PYTHON_VERSION: 3.8
     strategy:
       matrix:
         macos-py27:

.azure-pipelines/templates/steps/tox-steps.yml

@@ -21,7 +21,6 @@ steps:
     inputs:
       versionSpec: $(PYTHON_VERSION)
       addToPath: true
-    condition: ne(variables['PYTHON_VERSION'], '')
     # tools/pip_install.py is used to pin packages to a known working version
     # except in tests where the environment variable CERTBOT_NO_PIN is set.
     # virtualenv is listed here explicitly to make sure it is upgraded when
@@ -30,6 +29,7 @@ steps:
     # set, pip updates dependencies it thinks are already satisfied to avoid some
     # problems with its lack of real dependency resolution.
   - bash: |
+      python letsencrypt-auto-source/pieces/pipstrap.py
       python tools/pip_install.py -I tox virtualenv
     displayName: Install runtime dependencies
   - task: DownloadSecureFile@1

tox.ini

@@ -7,12 +7,11 @@ skipsdist = true
 envlist = modification,py3-cover,lint,mypy
 
 [base]
-# pip installs the requested packages in editable mode
-pip_install = python {toxinidir}/tools/pip_install_editable.py
 # pip installs the requested packages in editable mode and runs unit tests on
 # them. Each package is installed and tested in the order they are provided
 # before the script moves on to the next package. All dependencies are pinned
 # to a specific version for increased stability for developers.
+pip_install = python {toxinidir}/tools/pip_install_editable.py
 install_and_test = python {toxinidir}/tools/install_and_test.py
 dns_packages =
     certbot-dns-cloudflare \
@@ -62,6 +61,7 @@ source_paths =
 [testenv]
 passenv =
     CERTBOT_NO_PIN
+commands_pre = python {toxinidir}/letsencrypt-auto-source/pieces/pipstrap.py
 commands =
     !cover: {[base]install_and_test} {[base]all_packages}
     !cover: python tests/lock_test.py