[Answered ]-Django TemplateSyntaxError: Template library bootstrap3 not found

Please recheck “bootstrap3” in your INSTALLED_APPS and restart django. New template tags will be added only after restart.

In my case the problem was filesystem permissions.

I’m running as a normal user on CentOS 7, but Apache runs in daemon mode as user:apache group:apache. After doing a pip install bootstrap3, I forgot to do a sudo chown -R :apache /srv/python, where /srv/python/.../site-packages is on the python-path configured in WSGIDaemonProcess. Making the newly-loaded site-package readable by group :apache and restarting httpd fixed the problem.