Update appveyor config

Author: sdispater

appveyor.yml

@@ -21,14 +21,15 @@ install:
   # Create poetry virtualenv
   - pip install virtualenv
   - virtualenv --python="C:/Python36-x64\\python.exe" "venv-poetry"
+  - venv-poetry\\Scripts\\pip.exe install poetry --pre
 
   # Create current python virtualenv
   - "virtualenv --python=%PYTHON%\\python.exe venv"
   - venv\\Scripts\\activate.bat
+  - python --version
 
   # Install dependencies
   - pip install codecov
-  - venv-poetry\\Scripts\\pip.exe install poetry --pre
   - venv-poetry\\Scripts\\poetry.exe install -v
 
 test_script: