M PyShell.py

M PyShell.py
1. Format and print exceptions raised in user code.

M rpc.py
1. Additional debug messages in rpc.py
2. Move debug message enable switch from SocketIO to Client and Server
   to allow separate activation.
3. Add indication of origin (client or server) to debug message
4. Add sequence number to appropriate debug messages

5. Pass string exception arg as a string rather than a tuple.