Remove pytest-env

* We were using the pytest-env plugin to run the tests in a non-UTC time zone.
* The pytest-env plugin doesn't work with pytest-xdist so this was being ignored.
* Also due to the way TZ support works in Python, changing the env var whilst Python is running may or may not result in changes.

.github/workflows/test_fast.yml

@@ -20,11 +20,17 @@ jobs:
       fail-fast: false # Don't let a failed MacOS run stop the Ubuntu runs
       matrix:
         os: ['ubuntu-latest']
-        python-version: ['3.7', '3.8', '3.9', '3.10', '3.11']
+        python-version: ['3.7', '3.8', '3.10', '3.11']
         include:
+          # mac os test
           - os: 'macos-latest'
-            python-version: '3.7'
+            python-version: '3.7'  # oldest supported version
+          # non-utc timezone test
+          - os: 'ubuntu-latest'
+            python-version: '3.9'  # not the oldest, not the most recent version
+            time-zone: 'XXX-09:35'
     env:
+      TZ: ${{ matrix.time-zone }}
       PYTEST_ADDOPTS: --cov --cov-append -n 5 --color=yes
     steps:
       - name: Checkout

pytest.ini

@@ -32,9 +32,6 @@ testpaths =
     cylc/flow/
     tests/unit/
     tests/integration/
-env =
-    # a weird timezone to check that tests aren't assuming the local timezone
-    # TZ=XXX-09:35
 doctest_optionflags =
     NORMALIZE_WHITESPACE
     IGNORE_EXCEPTION_DETAIL

setup.cfg

@@ -119,7 +119,6 @@ tests =
     pytest-asyncio>=0.17,!=0.23.*
     pytest-cov>=2.8.0
     pytest-xdist>=2
-    pytest-env>=0.6.2
     pytest>=6
     testfixtures>=6.11.0
     towncrier>=23