Publish artifacts from test_output on CI fail (#372)

When trying to debug tests on the Github CI, the output from
pytest is often insufficient because some errors are written to
the redirected stderr and stdout of launched applications. This
PR uploads the test_output directory as an artifact of the
workflow on failure.

[ committed by @ashao ]
[ reviewed by @al-rigazzi , @MattToast ]

.github/workflows/run_tests.yml

@@ -133,6 +133,20 @@ jobs:
           echo "SMARTSIM_LOG_LEVEL=debug" >> $GITHUB_ENV
           py.test -s --import-mode=importlib -o log_cli=true --cov=$(smart site) --cov-report=xml --cov-config=./tests/test_configs/cov/local_cov.cfg --ignore=tests/full_wlm/ ./tests/
 
+      # Upload artifacts on failure, ignoring binary files
+      - name: Upload Artifact
+        if: failure()
+        uses: actions/upload-artifact@v3
+        with:
+          name: test_artifact
+          path: |
+            tests/test_output
+            !**/*.so
+            !**/*.pb
+            !**/*.pt
+            !**/core
+          retention-days: 5
+
       - name: Upload Pytest coverage to Codecov
         uses: codecov/codecov-action@v2
         with: