appveyor: update/install pip, setuptools and wheel
So wheels can be built for requirements that are installed from source.
@@ -18,6 +18,7 @@ environment:
install:
- "SET PATH=%PYTHON%;%PYTHON%\\Scripts;%PATH%"
- "python --version"
+ - "python -m pip install --upgrade --disable-pip-version-check pip setuptools wheel"
- "pip install --upgrade certifi tox tox-venv"
- "pip freeze --all"
# Fix git SSL errors.
