add libraw to workflow explicit install statement

.github/workflows/pythonapp.yml

@@ -16,7 +16,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install numpy cython
+        pip install numpy cython libraw
         pip3 install -r requirements.txt
     - name: Lint with flake8
       run: |