Cache pip dependencies

.github/workflows/python-sanity.yaml

@@ -4,7 +4,7 @@ on: [pull_request]
 
 jobs:
   build:
-
+    name: Running sanity tests
     runs-on: ubuntu-latest
     strategy:
       fail-fast: false
@@ -18,9 +18,22 @@ jobs:
       with:
         python-version: ${{ matrix.python-version }}
 
-    - name: Install dependencies
+    - name: Get pip cache dir
+      id: pip-cache
       run: |
         python -m pip install --upgrade pip
+        echo "::set-output name=dir::$(pip cache dir)"
+
+    - name: pip cache
+      uses: actions/cache@v2
+      with:
+        path: ${{ steps.pip-cache.outputs.dir }}
+        key: ${{ runner.os }}-pip-${{ matrix.python-version }}-${{ hashFiles('**/requirements-dev.txt') }}
+        restore-keys: |
+          ${{ runner.os }}-pip-${{ matrix.python-version }}-
+
+    - name: Install dependencies
+      run: |
         pip install -r requirements-dev.txt
 
     - name: Lint with flake8