python - NameError: name 'hasattr' is not defined - Python3.6, Django1.11, Ubuntu16-17, Apache2.4, mod_wsgi

Question

I've set up my Python/Django virtual environment, and mod_wsgi in daemon mode, and am pretty sure (done this before) it's "mostly correct" except I get the following error...

[Thu Jul 06 00:35:26.986363 2017] [mpm_event:notice] [pid 11442:tid 140557758930432] AH00493: SIGUSR1 received.  Doing graceful restart
Exception ignored in: <object repr() failed>
Traceback (most recent call last):
  File "/home/jamin/www/dev.tir.com/py361ve/lib/python3.6/site-packages/PIL/Image.py", line 572, in __del__
NameError: name 'hasattr' is not defined
[Thu Jul 06 00:35:27.194483 2017] [mpm_event:notice] [pid 11442:tid 140557758930432] AH00489: Apache/2.4.25 (Ubuntu) mod_wsgi/4.5.15 Python/3.6 configured -- resuming normal operations
[Thu Jul 06 00:35:27.194561 2017] [core:notice] [pid 11442:tid 140557758930432] AH00094: Command line: '/usr/sbin/apache2'

My django app itself is loading fine through wsgi.py but it seems something to do with core python (error with my setup likely) is going wrong as per: NameError: name 'hasattr' is not defined

In the browser - I get a plain "Server Error (500)" page and not the standard Apache "Internal Server Error" page.

Leaving out my VirtualHost and steps beyond here are the basic steps I put together for myself if you can spot anything... (I've tried all the different python packages as well not just -venv)

Install Python 3.6 and virtualenv
    sudo apt-get update
    sudo apt-get install python3.6-venv
    sudo apt-get install virtualenv
(or find the latest and greatest python package that includes pip https://packages.ubuntu.com/ )


Install Apache2
    sudo apt-get install apache2 apache2-dev


Make and enter a folder for your project - then build a Virtual Environment in it
    mkdir ~/example.com
    cd ~/example.com
    virtualenv --python=/usr/bin/python3.6 py361ve

Enter your new Virtual Environment to install packages to it
    source py361ve/bin/activate

Install Django, mod_wsgi, and any other needed packages
    pip install django
    pip install mod_wsgi
    pip install ...
(no need for pip3 in virtual environment - django should be the latest release)


Run following command and place output in apache config file ( in /etc/apache2/ )
    mod_wsgi-express module-config


Exit your virtual environment
    deactivate
(You can re-enter your virtual environment any time using the source method in step 8)

Here's what happens when I stop/start/restart apache2...

apache2 stop...

[Thu Jul 06 06:01:34.190940 2017] [mpm_event:notice] [pid 2015:tid 140157449797120] AH00491: caught SIGTERM, shutting down
_______________________________________________________________
apache2 start...

[Thu Jul 06 06:02:39.076741 2017] [mpm_event:notice] [pid 2181:tid 140553545080320] AH00489: Apache/2.4.25 (Ubuntu) mod_wsgi/4.5.15 Python/3.6 configured -- resuming $
[Thu Jul 06 06:02:39.076890 2017] [core:notice] [pid 2181:tid 140553545080320] AH00094: Command line: '/usr/sbin/apache2'
_______________________________________________________________
apache2 restart...

Exception ignored in: <object repr() failed>
Traceback (most recent call last):
  File "/home/jamin/www/dev.tir.com/py361ve/lib/python3.6/site-packages/PIL/Image.py", line 572, in __del__
NameError: name 'hasattr' is not defined
[Thu Jul 06 06:05:43.307877 2017] [mpm_event:notice] [pid 2181:tid 140553545080320] AH00491: caught SIGTERM, shutting down
[Thu Jul 06 06:05:43.492499 2017] [mpm_event:notice] [pid 2301:tid 140353155558912] AH00489: Apache/2.4.25 (Ubuntu) mod_wsgi/4.5.15 Python/3.6 configured -- resuming $
[Thu Jul 06 06:05:43.492705 2017] [core:notice] [pid 2301:tid 140353155558912] AH00094: Command line: '/usr/sbin/apache2'

Answer 1

This is likely due to code still running in background threads when the Python interpreter is being destroyed on process shutdown. What happens during interpreter destruction is that all modules get wiped out and attribute access of things often returns None as fallback. In this case looks like builtins module was wiped before the PIL object got destroyed and so it couldn't find hasattr.

Can you confirm this only happens when Apache is being restarted and processes shutdown?