Travis CI: Test Python 3.9 release candidate 1 (celery#6328)

* Travis CI: Test Python 3.9 release candidate 1

* fixup! Travis CI: matrix --> jobs

* fixup! Fix indentation error

* fixup! tox.ini: 3.9 --> 3.9-dev

* Fix test failure in Python 3.9RC1.

Co-authored-by: Omer Katz <omer.drow@gmail.com>

.travis.yml

@@ -5,22 +5,32 @@ python:
   - '3.6'
   - '3.7'
   - '3.8'
+  - '3.9-dev'
 os:
     - linux
 stages:
   - test
   - integration
   - lint
+services:
+  - redis
+  - docker
 env:
   global:
   - PYTHONUNBUFFERED=yes
   - CELERY_TOX_PARALLEL=
-  matrix:
+  jobs:
   - MATRIX_TOXENV=unit
 
-matrix:
+jobs:
   fast_finish: true
+  allow_failures:
+  - python: '3.9-dev'
   include:
+  - python: '3.9-dev'
+    env: MATRIX_TOXENV=integration-rabbitmq
+    stage: integration
+
   - python: 3.8
     env: MATRIX_TOXENV=integration-rabbitmq
     stage: integration
@@ -112,21 +122,18 @@ before_install:
           wget -qO - https://packages.couchbase.com/ubuntu/couchbase.key | sudo apt-key add -
           sudo apt-add-repository -y 'deb http://packages.couchbase.com/ubuntu bionic bionic/main'
           sudo apt-get update && sudo apt-get install -y libcouchbase-dev
+install: pip --disable-pip-version-check install --upgrade-strategy eager -U tox | cat
+script: tox $CELERY_TOX_PARALLEL -v -- -v
 after_success:
   - |
           if [[ -v MATRIX_TOXENV || "$TOXENV" =~ "pypy" ]]; then
               .tox/$TOXENV/bin/coverage xml
               .tox/$TOXENV/bin/codecov -e TOXENV
           fi;
-install: pip --disable-pip-version-check install --upgrade-strategy eager -U tox | cat
-script: tox $CELERY_TOX_PARALLEL -v -- -v
 notifications:
   email: false
   irc:
     channels:
       - "chat.freenode.net#celery"
     on_success: change
     on_failure: change
-services:
-    - redis
-    - docker

celery/canvas.py

@@ -440,6 +440,12 @@ def __or__(self, other):
             return _chain(self, other, app=self._app)
         return NotImplemented
 
+    def __ior__(self, other):
+        # Python 3.9 introduces | as the merge operator for dicts.
+        # We override the in-place version of that operator
+        # so that canvases continue to work as they did before.
+        return self.__or__(other)
+
     def election(self):
         type = self.type
         app = type.app

tox.ini

@@ -1,7 +1,7 @@
 [tox]
 envlist =
-    {3.6,3.7,3.8,pypy3}-unit
-    {3.6,3.7,3.8,pypy3}-integration-{rabbitmq,redis,dynamodb,azureblockblob,cache,cassandra,elasticsearch}
+    {3.6,3.7,3.8,3.9-dev,pypy3}-unit
+    {3.6,3.7,3.8,3.9-dev,pypy3}-integration-{rabbitmq,redis,dynamodb,azureblockblob,cache,cassandra,elasticsearch}
 
     flake8
     apicheck
@@ -14,9 +14,9 @@ deps=
     -r{toxinidir}/requirements/test.txt
     -r{toxinidir}/requirements/pkgutils.txt
 
-    3.6,3.7,3.8: -r{toxinidir}/requirements/test-ci-default.txt
-    3.5,3.6,3.7,3.8: -r{toxinidir}/requirements/docs.txt
-    3.6,3.7,3.8: -r{toxinidir}/requirements/docs.txt
+    3.6,3.7,3.8,3.9-dev: -r{toxinidir}/requirements/test-ci-default.txt
+    3.5,3.6,3.7,3.8,3.9-dev: -r{toxinidir}/requirements/docs.txt
+    3.6,3.7,3.8,3.9-dev: -r{toxinidir}/requirements/docs.txt
     pypy3: -r{toxinidir}/requirements/test-ci-base.txt
 
     integration: -r{toxinidir}/requirements/test-integration.txt
@@ -63,6 +63,7 @@ basepython =
     3.6: python3.6
     3.7: python3.7
     3.8: python3.8
+    3.9-dev: python3.9
     pypy3: pypy3
     flake8,apicheck,linkcheck,configcheck,bandit: python3.8
     flakeplus: python2.7