Adding missing dep

Signed-off-by: Cédric Foellmi <cedric@onekiloparsec.dev>

Author: onekiloparsec

.github/workflows/tests.yml

@@ -25,7 +25,7 @@ jobs:
         run: |
           python -m pip install --upgrade pip
           if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
-          pip install pytest pytest-cov
+          pip install pytest pytest-cov responses
           pip install -e .
 
       - name: Test with pytest