Explicitly set up Python 2 for the test262 test run.

.github/workflows/ci.yml

@@ -39,14 +39,21 @@ jobs:
         strategy:
             fail-fast: false
             matrix:
-                os: [ubuntu-latest]
+                os: [ubuntu-20.04]
                 dc: [dmd-latest]
                 arch: [x86_64]
 
         runs-on: ${{ matrix.os }}
+            container:
+                image: python:2.7.18-buster
         steps:
             - uses: actions/checkout@v2
 
+            - name: Set up Python 2
+              uses: actions/setup-python@v5
+              with:
+                python-version: 2.7.18
+
             - name: Install D compiler
               uses: dlang-community/setup-dlang@v1
               with: