Add a way to debug github CI

.github/workflows/build.yml

@@ -1,6 +1,14 @@
 name: Build
 
-on: [push, pull_request]
+on:
+  push:
+  pull_request:
+  workflow_call:
+    inputs:
+      debug_ssh_session:
+        required: false
+        type: boolean
+
 
 env:
   PYTEST_ADDOPTS: --color=yes
@@ -18,6 +26,11 @@ jobs:
       run: |
         python -m pip install --upgrade pip setuptools wheel
         pip install .[qa] .[testing]
+    - name: Setup tmate session
+      uses: mxschmitt/action-tmate@v3
+      if: ${{ inputs.debug_ssh_session }}
+      with:
+        limit-access-to-actor: true
     - name: Run Flake8
       # Ignore F401, which are unused imports. flake8 is a primitive tool and is sometimes wrong.
       run: flake8 --extend-ignore F401 parso test/*.py setup.py scripts/