Add extra libxcb package required by the newest PySide6 versions (#1741)

This PR adds `libxcb-image0` to the list of packages that are `apt-get`
installed in the various GitHub Actions workflows. The `libxcb-image0`
package is needed for the latest PySide6 versions.

EDIT: Updated to also address failures due to the qt4 / qt switch in
Pyface.

Closes #1742.

.github/workflows/run-traits-tests.yml

@@ -4,6 +4,11 @@ on:
 - pull_request
 - workflow_dispatch
 
+env:
+  # Temporary workaround prior to release of Traits 8.0
+  # xref: enthought/traits#1742
+  ETS_QT4_IMPORTS: 1
+
 jobs:
   tests:
     strategy:
@@ -20,6 +25,7 @@ jobs:
         sudo apt-get update
         sudo apt-get install libegl1
         sudo apt-get install libxkbcommon-x11-0
+        sudo apt-get install libxcb-cursor0
         sudo apt-get install libxcb-icccm4
         sudo apt-get install libxcb-image0
         sudo apt-get install libxcb-keysyms1

.github/workflows/test-from-pypi.yml

@@ -6,6 +6,11 @@ on:
     # Run at 03:27 UTC on the 8th and 22nd of every month
     - cron: '27 3 8,22 * *'
 
+env:
+  # Temporary workaround prior to release of Traits 8.0
+  # xref: enthought/traits#1742
+  ETS_QT4_IMPORTS: 1
+
 jobs:
   test-pypi-sdist:
     strategy:
@@ -27,6 +32,7 @@ jobs:
         sudo apt-get update
         sudo apt-get install libegl1
         sudo apt-get install libxkbcommon-x11-0
+        sudo apt-get install libxcb-cursor0
         sudo apt-get install libxcb-icccm4
         sudo apt-get install libxcb-image0
         sudo apt-get install libxcb-keysyms1
@@ -77,6 +83,7 @@ jobs:
         sudo apt-get update
         sudo apt-get install libegl1
         sudo apt-get install libxkbcommon-x11-0
+        sudo apt-get install libxcb-cursor0
         sudo apt-get install libxcb-icccm4
         sudo apt-get install libxcb-image0
         sudo apt-get install libxcb-keysyms1