If you are running Django under mod_wsgi on apache you might see errors like "IOError: failed to write data" followed by "Exception occurred processing WSGI script" in your logs, this is because your code is actually throwing an exception but Django likes to hide any errors from your users...
_wsgi (pid=6475): Target WSGI script '/opt/flask-reload-issue/flask_reload_issue.wsgi' cannot be loaded as Python module. [Mon Apr 24 09:31:27.956311 2017] [:error] [pid 6475:tid 140343668315904] [remote 10.0.2.2:44628] mod_wsgi (pid=6475): Exception occurred processing WSGI script '...