Select py3 for edge stable runs
diff --git a/.azure-pipelines.yml b/.azure-pipelines.yml
index cbd7b33..308a684 100644
--- a/.azure-pipelines.yml
+++ b/.azure-pipelines.yml
@@ -489,6 +489,9 @@
   pool:
     name: 'Hosted Windows Client'
   steps:
+  - task: UsePythonVersion@0
+    inputs:
+      versionSpec: '3.6.x'
   - template: tools/ci/azure/system_info.yml
   - template: tools/ci/azure/checkout.yml
   - template: tools/ci/azure/install_python.yml
diff --git a/tools/ci/azure/update_manifest.yml b/tools/ci/azure/update_manifest.yml
index 453ac2a..c09b04d 100644
--- a/tools/ci/azure/update_manifest.yml
+++ b/tools/ci/azure/update_manifest.yml
@@ -1,4 +1,6 @@
 steps:
 # `python wpt` instead of `./wpt` is to make this work on Windows:
-- script: python wpt manifest
+- script: |
+    python --version
+    python wpt manifest
   displayName: 'Update manifest'