[ci] Repeat failed tests without the parallel flag (subtest issue)

Repeat tests withtout the parallel flag because subtests do not get pickled correclty in parallel tests.

Author: nemesifier

.github/workflows/ci.yml

@@ -87,9 +87,10 @@ jobs:
     - name: Tests
       if: ${{ !cancelled() && steps.deps.conclusion == 'success' }}
       run: |
-        coverage run runtests.py --parallel
+        coverage run runtests.py --parallel || coverage run ./runtests.py
         # tests the extension capability
-        SAMPLE_APP=1 coverage run ./runtests.py --parallel --keepdb --exclude-tag=selenium_tests
+        SAMPLE_APP=1 coverage run ./runtests.py --parallel --keepdb --exclude-tag=selenium_tests \
+          || SAMPLE_APP=1 coverage run ./runtests.py --keepdb --exclude-tag=selenium_tests
         coverage combine
         coverage xml
       env: