parser module is removed from python 3.10

Just FYI:

The `parser` module is removed from python3.10. The [docs](https://docs.python.org/3.9/library/parser.html) suggests using the `ast` module.
See [`PyDSTool/parseUtils.py`](https://github.com/robclewley/pydstool/blob/master/PyDSTool/parseUtils.py)