_shutdown AttributeError (ignored) when linting code that uses M2Crypto

Asked 2011-09-04T23:32:12.453

I'm running lint as follows:

$ python -m pylint.lint m2test.py

with this code:

import M2Crypto
def f():
    M2Crypto.RSA.new_pub_key("").as_pem(cipher=None).split("\n")

The lint output ends with:

Exception AttributeError: '_shutdown' in <module 'threading' from '/usr/lib/python2.7/site-packages/M2Crypto-0.21.1-py2.7-linux-x86_64.egg/M2Crypto/threading.pyc'> ignored

This code works fine when run (the above is actually a minimal test case; but the full version does work). The exception is ignored, but Bitten considers this a failure, so stops on this step.

I've tried adding 'M2Crypto.threading.init()'/'M2Crypto.threading.cleanup()' around the definition of the function, but that didn't fix the problem.

How can I prevent this problem from occurring?

I'm using M2Crypto 0.21.1, pylint 0.24 and Python 2.7 (also tried 2.7.2) on Debian Lenny x86_64.

python m2crypto pylint

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2 Answers

The exception that you are seeing is caused by a bug in the astng package (presumably “Abstract Syntax Tree, Next Generation”?) which is a toolkit on which pylint depends, written by the same people. I should note in passing that I always encourage people to use pyflakes instead of pylint when possible, because it is quick, simple, fast, and predictable, whereas pylint tries to do several kinds of deep magic that are not only slow but that can get it into exactly this kind of trouble. :)

Here are the two packages on PyPI:

http://pypi.python.org/pypi/pylint

http://pypi.python.org/pypi/astng

And note that this problem had to be, necessarily, a bug in pylint and not in your code, because pylint does not run your code in order to produce its report — imagine the havoc that could be wreaked if it did (since code being linted might delete files, etcetera)! Since your code does not get run, no amount of caution, like protecting your call with threading init() or cleanup() functions, could possibly have prevented this error — unless the code snippets happened, for other reasons, to alter the behavior we are about to investigate.

So, on to your actual exception.

I had never actually heard of _shutdown before! A quick search of the Python standard library showed its definition in threading.py but not a call of the function from anywhere; only by searching the Python C source code did I discover where in pythonrun.c, during interpreter shutdown, the function is actually called:

static void
wait_for_thread_shutdown(void)
{
    ...
    PyObject *threading = PyMapping_GetItemString(tstate->interp->modules,


                        
                        
                            answered 2011-09-14T02:06:07.333


            
            
                
                    
                        
                            
                            
                        
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                        This looks more like a hack but I think it works. Copying the result of "as_pem()" and splitting it.

import M2Crypto
def f():
    M2Crypto.RSA.new_pub_key("").as_pem(cipher=None)[:].split("\n")


I'm using Python 2.6.7, M2Crypto 0.21.1, pylint 0.23

                        
                        
                            answered 2011-09-13T05:54:44.497



        
        
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