fixup! Using sep-pjw as substitute for sep

.github/workflows/coverage.yml

@@ -21,7 +21,7 @@ jobs:
       - name: Install coverage
         run: pip install coverage
       - name: Install astroalign dependencies
-        run: pip install "numpy>=1.11" "scipy>=0.15" scikit-image sep
+        run: pip install "numpy>=1.11" "scipy>=0.15" scikit-image sep-pjw
       - name: Install test dependencies
         run: pip install -r tests/requirements.txt
       - name: Run coverage