CI Python package install

For continuous integration, it’s important to test the traditional package install

pip install .

along with the more commonly used in situ pip development mode

pip install -e .

Otherwise, the Python package install may depend on files not included in the file and fail for most end users who don’t use “pip install -e” option.

A particular failure this will catch on Windows CI is graft path/to/ where the trailing / will fail on Windows only.