Pin to oldest supported PyQt on minver CI instance.

anntzer · anntzer · commit 977955cdeff3 · 2021-01-18T11:41:23.000+01:00
This will be relevant once we also include PyQt6 support, as details of
enum access have changed in PyQt 5.11.

PyQt is not actually a dependency so I don't think we can use the
constraints file (minver.txt) for that.
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
@@ -25,6 +25,7 @@ jobs:
             os: ubuntu-16.04
             python-version: 3.7
             extra-requirements: '-c requirements/testing/minver.txt'
+            pyqt5-ver: 5.8  # oldest version with a Py3.7 wheel.
             delete-font-cache: true
             XVFB_RUN: xvfb-run -a
           - os: ubuntu-16.04
@@ -168,7 +169,7 @@ jobs:
             # Sept 2020) for either pyqt5 (there are only wheels for 10.13+) or
             # pyside2 (the latest version (5.13.2) with 10.12 wheels has a
             # fatal to us bug, it was fixed in 5.14.0 which has 10.13 wheels)
-             python -mpip install --upgrade pyqt5 &&
+             python -mpip install --upgrade pyqt5${{ matrix.pyqt5-ver }} &&
                python -c 'import PyQt5.QtCore' &&
                echo 'PyQt5 is available' ||
                echo 'PyQt5 is not available'
