bug#61463: 29.0.60; python-shell-send-region moves point

[Augusto Stoffel]

On Emacs -Q:

1) M-x run-python
2) In the scratch buffer, type something, say 1 + 2 and mark it, leaving
   point at the end.
3) M-x python-shell-send-string

Now the point is at the beginning of the region.  It was supposed not to
move.

I suspect this might be due to a missing `save-excursion' in the
definition of the local variable `single-p' in python.el.