Never mind. I discovered it was an import I was using (pexpect) that is catching all exceptions.
I am actually trying to debug a much larger module and it quits without telling me anything, even a line number, so I have to set breakpoints, run, if it hits it set another breakpoint farther down, if it DOESN'T hit it, set another breakpoint further up and restart. VERY tedious.
I have reproduced the problem with this trivial code:
x = 7
y = z
Note that 'z' has not been initialized. If I try to run this in PyCharm it terminates and the console screen shows:
Process finished with exit code 1
It doesn't give any error message at all. Knowing me, it's probably some config error I've made, but it is a pretty fresh install of PyCharm community edition (4.0.4).