[Cherrypy-users] Re: Exception in tests of CherryPy-2.1.0

[Peter H. <pe...@en...>]

T. S. Ferreira wrote:
> I installed version 2.1.0 and ran the test suite. Everything went fine 
> but at the end I got the message:
> -----------------------------------
> Unhandled exception in thread started by
> Error in sys.excepthook:
> 
> Original exception was:
> -----------------------------------
> 
> My system is Linux Fedora Core 4, and Python 2.4.1.
> 
> Any hints?

This looks very much like the (not widely) known problem of shutting 
down the python interpreter while a daemon thread is still running. 
What happens is the main thread exits (because only daemon threads are 
left running), and then the interpreter walks through everything in 
sys.modules and rebinds all module global names to None.  While it's 
doing this (a process which is pretty quick, but not instantaneous), the 
daemon thread(s) might have a chance to run again for a moment, and if 
the running one tries to access one of its globals, it usually raise an 
exception because of the None-substitution.

One alternative for you is to close your eyes briefly after the test 
completes, type "clear" or "cls", re-open your eyes and carry on as 
though nothing happened.  I do that most of the time.

Another solution is to modify the code so that threads are properly 
terminated.  Depending on the code in question this can be either 
trivial (e.g. a simple "time.sleep()" *might* be enough, but only if the 
daemon threads are already on their way to stopping themselves but just 
need a little extra time), or it can be quite a lot of work (modifying 
lots of code to replace the threads with your own StoppableThread class, 
or whatever...).

In the end, this sort of thing is basically harmless, although an 
annoying wart.

-Peter