* Update grpcio to a version that provides darwin arm64 builds
No more compiling of grpcio on an M1 macbook.
* Remove system version compatibility flag during bootstrap
We're long on versions that work on all recent (and supported) MacOS
versions.
* Check for a valid python installation
* Actually exit if `venv` directory already exists
* Don't require virtualenv package (use `venv` builtin)
* Ensure that we don't attempt to recompile numpy or pandas when
installing on more recent versions of Mac
This simplifies the multiple choice installation process into
a simplified version which uses a local virtualenv, which will
hopefully be easier to support and debug.
Jan-Erik Rediger
Daniel Thorn
Will Lachance