Flip ensure-tox to tox v4 by default

The previous change added a bunch of tox v4 compatiblity, now we switch
to as our default. This should only happen after people have had
sufficient time to add tox v4 compatibility or manually pin back to <4
in their projects.

Change-Id: I16742fb933dba2162a73d532e1a9613af69021aa

roles/ensure-tox/README.rst

@@ -6,13 +6,12 @@ virtual environment for the current user.
 **Role Variables**
 
 .. zuul:rolevar:: ensure_tox_version
-   :default: '<4'
+   :default: ''
 
    Version specifier to select the version of tox. For example if your
    project is not compatible with tox v4 you can set this value to
-   `<4` to install the latest v3 release. We have started this value
-   at `<4` for maximum compatibility, but expect it to change to ''
-   in the future when tox v4 is better understood.
+   `<4` to install the latest v3 release. The default is '' which
+   installs latest.
 
 .. zuul:rolevar:: tox_prefer_python2
    :default: False

roles/ensure-tox/defaults/main.yaml

@@ -1,5 +1,5 @@
 tox_executable: tox
-ensure_tox_version: '<4'
+ensure_tox_version: ''
 tox_venv_path: '{{ ansible_user_dir }}/.local/tox'
 tox_prefer_python2: false
 ensure_global_symlinks: false

test-playbooks/python/fetch-tox-output.yaml

@@ -56,14 +56,14 @@
   post_tasks:
     - name: Check for artifact on the test instance
       stat:
-        path: "{{ ansible_user_dir }}/zuul-output/logs/tox/venv/venv-0.log"
+        path: "{{ ansible_user_dir }}/zuul-output/logs/tox/venv/1-install_package.log"
       register: _test_artifact
       failed_when: not _test_artifact.stat.exists
       when: zuul_use_fetch_output
 
     - name: Check for artifact on the executor
       stat:
-        path: "{{ zuul.executor.log_root }}/tox/venv/venv-0.log"
+        path: "{{ zuul.executor.log_root }}/tox/venv/1-install_package.log"
       delegate_to: localhost
       register: _executor_artifact
       failed_when: not _executor_artifact.stat.exists

test-playbooks/python/tox.yaml

@@ -76,12 +76,22 @@
           register: ALL_status
           failed_when: ALL_status is changed
 
+    - name: Move test-playbooks/python/tox.ini to test-playbooks/python/foo.ini
+      # Tox 4 appears to have trouble when there is a tox.ini in the current
+      # dir and you run it with -c pointing at another file. Work around this
+      # to test the use of -c by moving the tox.ini to another location
+      # and -c'ing against that in the next task.
+      command: mv tox.ini foo.ini
+      args:
+        chdir: "{{ zuul.project.src_dir }}/test-playbooks/python/"
+
     - name: Run tox against a specific config file
       include_role:
         name: tox
       vars:
+        zuul_work_dir: "{{ zuul.project.src_dir }}/test-playbooks/python/"
         # Make sure the tox_config_file option works
-        tox_config_file: test-playbooks/python
+        tox_config_file: foo.ini
         tox_envlist: 'foo'
         # Make sure we test with verbose output even if the default changes
         tox_extra_args: '-vv'

zuul-tests.d/python-jobs.yaml

@@ -350,6 +350,7 @@
     description: Test the tox role's sibling functionality
     files:
       - roles/tox/.*
+      - roles/ensure-tox/.*
       - tox.ini
       - test-playbooks/python/tox.yaml
       - test-playbooks/python/tox.ini