i18n: Pull translations via GitHub Actions automatically

.github/workflows/transifex.yml

@@ -1,4 +1,4 @@
-name: Push translations to transifex.com
+name: Sync translations on repository and transifex.com
 
 on:
   schedule:
@@ -6,7 +6,7 @@ on:
   workflow_dispatch:
 
 jobs:
-  build:
+  push:
     runs-on: ubuntu-latest
 
     steps:
@@ -23,3 +23,29 @@ jobs:
       run:  cd sphinx/locale && tx push -s --no-interactive --parallel
       env:
         TX_TOKEN: ${{ secrets.TX_TOKEN }}
+
+  pull:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+      with:
+        ref: 4.x
+    - name: Set up Python
+      uses: actions/setup-python@v2
+    - name: Install dependencies
+      run:  pip install -U babel jinja2 transifex-client
+    - name: Extract translations from source code
+      run:  python setup.py extract_messages
+    - name: Pull translations to transifex.com
+      run:  cd sphinx/locale && tx pull -a -f --no-interactive --parallel
+      env:
+        TX_TOKEN: ${{ secrets.TX_TOKEN }}
+    - name: Compile message catalogs
+      run:  python setup.py compile_catalog
+    - name: Create Pull Request
+      uses: peter-evans/create-pull-request@v3
+      with:
+        commit-message: 'Update message catalogs'
+        branch: bot/pull-translations
+        title: Update message catalogs