Install signal handler on each code run to protect against user code that may modify it as well.  If we don't do this, on the next Ctrl-C python itself will likely just crash completely.
Install signal handler on each code run to protect against user code that
may modify it as well.  If we don't do this, on the next Ctrl-C python
itself will likely just crash completely.

ipython/ipython,ipython/ipython