Move to Python 3.9

Synapse require 3.9 since https://github.com/element-hq/synapse/pull/17908

.github/workflows/nightly.yml

@@ -16,10 +16,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - name: Set up Python 3.8
-        uses: actions/setup-python@v4
+      - name: Set up Python 3.9
+        uses: actions/setup-python@v5
         with:
-          python-version: 3.8
+          python-version: 3.9
       - name: Use JDK 21
         uses: actions/setup-java@v4
         with:

.github/workflows/post-pr.yml

@@ -40,10 +40,10 @@ jobs:
     # No concurrency required, runs every time on a schedule.
     steps:
       - uses: actions/checkout@v4
-      - name: Set up Python 3.8
-        uses: actions/setup-python@v4
+      - name: Set up Python 3.9
+        uses: actions/setup-python@v5
         with:
-          python-version: 3.8
+          python-version: 3.9
       - name: Use JDK 21
         uses: actions/setup-java@v4
         with:

.github/workflows/sync-from-external-sources.yml

@@ -13,10 +13,10 @@ jobs:
     # No concurrency required, runs every time on a schedule.
     steps:
       - uses: actions/checkout@v4
-      - name: Set up Python 3.8
-        uses: actions/setup-python@v4
+      - name: Set up Python 3.9
+        uses: actions/setup-python@v5
         with:
-          python-version: 3.8
+          python-version: 3.9
       - name: Install Prerequisite dependencies
         run: |
           pip install BeautifulSoup4
@@ -40,10 +40,10 @@ jobs:
     # No concurrency required, runs every time on a schedule.
     steps:
       - uses: actions/checkout@v4
-      - name: Set up Python 3.8
-        uses: actions/setup-python@v4
+      - name: Set up Python 3.9
+        uses: actions/setup-python@v5
         with:
-          python-version: 3.8
+          python-version: 3.9
       - name: Install Prerequisite dependencies
         run: |
           pip install requests

.github/workflows/tests.yml

@@ -52,9 +52,9 @@ jobs:
             **/out/failures/
             **/build/reports/tests/*UnitTest/
 
-      - uses: actions/setup-python@v4
+      - uses: actions/setup-python@v5
         with:
-          python-version: 3.8
+          python-version: 3.9
       - uses: michaelkaye/setup-matrix-synapse@v1.0.5
         with:
           uploadLogs: true