Install tblib to fix tracebacks during parallel test runs

.github/workflows/ci.yml

@@ -56,7 +56,7 @@ jobs:
       run: |
         python -m pip install --upgrade pip
         pip install -r requirements.txt
-        pip install pycodestyle coverage
+        pip install pycodestyle coverage tblib
         ln -s configuration.testing.py netbox/netbox/configuration.py
 
     - name: Build documentation