trying to execute the following code:
import sys
def trace(frame, event, arg):
    if event == "line" and frame.f_lineno > 12:
        frame.f_lineno = 12
        return None
    return trace
sys.settrace(trace)
def error():
    try:
        pass
    except:
        pass
    pass
    pass
error()
Produces a fatal error:
Fatal Python error: XXX block stack underflow

Current thread 0x00000af4 (most recent call first):
  File "jumpintoexception.py", line 12 in error
  File "jumpintoexception.py", line 15 in <module>