mod_wsgi End of script output before headers

Question

I have a problem with my web application. Sometimes when people upload an image (seems to happen with large image only), I have mod_wsgi who crash with this message :

End of script output before headers: wsgi.py, referer:http:::...
Process 'wsgi' has died, restarting.
Process 'wsgi' terminated by signal 9

and so an internal error is raised.

Here is my wsgi file:

import os
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "settings")

from django.core.wsgi import get_wsgi_application
application = get_wsgi_application()

and here is the wsgi conf file

LoadModule wsgi_module modules/mod_wsgi.so
WSGIPythonHome /opt/python/run/baselinenv
WSGISocketPrefix run/wsgi
WSGIRestrictEmbedded On

<VirtualHost *:80>

Alias /static/ /opt/python/current/app/static/
<Directory /opt/python/current/app/static/>
Order allow,deny
Allow from all
</Directory>


WSGIScriptAlias / /opt/python/current/app/wsgi.py


<Directory /opt/python/current/app/>
  Require all granted
</Directory>

WSGIDaemonProcess wsgi processes=1 threads=15 display-name=%{GROUP} \
  python-path=/opt/python/current/app:/opt/python/run/venv/lib/python2.7/site-packages user=wsgi group=wsgi \
  home=/opt/python/current/app
WSGIProcessGroup wsgi
</VirtualHost>

Do you know what is the problem and what I can do to solve it ?

Please note that I cannot migrate to nginx and gunicorn.

Thanks a lot