Unfriendly trace if device resets

[JPHutchins]

If a command sent by smpmgr causes the device to assert or hard fault, a stack trace is printed out, ending with something like OSError: [Errno 5] Input/output error. These are likely diagnosable... but at the very least, the default message to the user should be something like "Whoops! Looks like the connection to the device was lost!" and the trace can be sent to the debug logs.