Update mystnb error reporting in CI

Author: timothymillar

.github/workflows/build.yml

@@ -38,7 +38,12 @@ jobs:
       if: failure()
       with:
         name: gwas_tutorial
-        path: /home/runner/work/sgkit/sgkit/docs/_build/html/reports/gwas_tutorial.log
+        path: /home/runner/work/sgkit/sgkit/docs/_build/html/reports/examples/gwas_tutorial.err.log
+    - uses: actions/upload-artifact@v2
+      if: failure()
+      with:
+        name: relatedness_tutorial
+        path: /home/runner/work/sgkit/sgkit/docs/_build/html/reports/examples/relatedness_tutorial.err.log
     - name: Test with pytest
       run: |
         pytest -v