Maybe GHA doesn't actually run apt-get update before runs...

Author: Julian

.github/workflows/ci.yml

@@ -162,7 +162,9 @@ jobs:
     - name: Ensure we have new enough versions to respect python_version
       run: python -m pip install -U pip setuptools
     - name: Install dependencies
-      run: sudo apt-get install -y libenchant-dev libxml2-dev libxslt-dev
+      run: >
+        sudo apt-get update
+        sudo apt-get install -y libenchant-dev libxml2-dev libxslt-dev
       if: runner.os == 'Linux' && startsWith(matrix.python-version.toxenv, 'docs-')
     - name: Install dependencies
       run: brew install enchant