github: try to get latest tools using pip

.github/workflows/python_checks.yml

@@ -15,9 +15,11 @@ jobs:
     - uses: actions/checkout@v1
       with:
         token: ${{ secrets.ACCESS_TOKEN }}
+    - name: Install Python3
+      run: sudo apt-get install python3 python3-setuptools python3-pip -y
     - name: Install tools
-      run: sudo apt-get install python-setuptools flake8 mypy -y
+      run: pip3 install --user mypy flake8
     - name: Check MAVSDK test scripts with mypy
-      run: mypy --strict test/mavsdk_tests/*.py
+      run: $HOME/.local/bin/mypy --strict test/mavsdk_tests/*.py
     - name: Check MAVSDK test scripts with flake8
-      run: flake8 test/mavsdk_tests/*.py
+      run: $HOME/.local/bin/flake8 test/mavsdk_tests/*.py