Use python -c to get the interpreter path hash

The current implementation has compatibility problems due to it using commands
only available on GNU Linux. Use an equivalent Python implementation for better
support on Windows and macOS.

See pypa/pip#7835.

Co-Authored-By: Xavier Fernandez <xavier.fernandez@polyconseil.fr>

README.md

@@ -25,7 +25,7 @@ jobs:
     - uses: actions/checkout@v1
     - uses: actions/setup-python@v1
     - name: set PY
-      run: echo "::set-env name=PY::$((python --version --version && which python) | sha256sum | cut -d' ' -f1)"
+      run: echo "::set-env name=PY::$(python -c 'import hashlib, sys;print(hashlib.sha256(sys.version.encode()+sys.executable.encode()).hexdigest())')"
     - uses: actions/cache@v1
       with:
         path: ~/.cache/pre-commit