The scripts in `Tools/peg_generator/scripts` mostly assume that
`ast.parse` and `compile` use the old parser, since this was the
state of things, while we were developing them. They need to be
updated to always use the correct parser. `_peg_parser` is being
extended to support both parsing and compiling with both parsers.
Create a `make venv` target, that creates a virtual environment
and installs the dependency in that venv. `make time` and all
the related targets are changed to use the virtual environment
python.
Automerge-Triggered-By: @pablogsal
Pablo Galindo
Lysandros Nikolaou
Anthony Shaw