The computation of `co_stacksize' by the compiler is known to give only an upper bound estimate.  http://bugs.python.org/issue1754094 is an example of fixing a "leak" where every repetition of a statement makes `co_stacksize' bigger by 1.  However, in the whole 3.x series (from at least 3.2), the following simple code, which at runtime requires about 4 or 5 stack slots, leaks 14(!) slots for every `try:' block.  Maybe this should be improved to reduce the extreme size of the leak.

def g():
    try: pass
    except ImportError as e: pass
    try: pass
    except ImportError as e: pass
    try: pass
    except ImportError as e: pass
    ...

i.e. any function that is big enough to contain 6 try: blocks in sequence will have its stack size overestimated by about 70.