title: GAE production + Django + Gunicorn Error: HaltServer 'Worker failed to boot.' 3
body: <p>I run my Django project on localhost by 'python manage.py runserver' - it works. 
  I deploy it on Google App Engine - on xxx.appspot.com it print <em>502 Bad Gateway/by Ngnix</em> and raise followed:</p>
  
  <p><strong>gunicorn.errors.HaltServer: </strong></p>
  
  <pre><code>    Traceback (most recent call last):
    File "/env/bin/gunicorn", line 10, in &lt;module&gt;
      sys.exit(run())
    File "/env/lib/python3.7/site-packages/gunicorn/app/wsgiapp.py", line 58, in run
      WSGIApplication("%(prog)s [OPTIONS] [APP_MODULE]").run()
    File "/env/lib/python3.7/site-packages/gunicorn/app/base.py", line 228, in run
      super().run()
    File "/env/lib/python3.7/site-packages/gunicorn/app/base.py", line 72, in run
      Arbiter(self).run()
    File "/env/lib/python3.7/site-packages/gunicorn/arbiter.py", line 229, in run
      self.halt(reason=inst.reason, exit_status=inst.exit_status)
    File "/env/lib/python3.7/site-packages/gunicorn/arbiter.py", line 342, in halt
      self.stop()
    File "/env/lib/python3.7/site-packages/gunicorn/arbiter.py", line 380, in stop
      and not self.cfg.reuse_port
    File "/env/lib/python3.7/site-packages/gunicorn/config.py", line 201, in reuse_port
      @property
    File "/env/lib/python3.7/site-packages/gunicorn/arbiter.py", line 242, in handle_chld
      self.reap_workers()
    File "/env/lib/python3.7/site-packages/gunicorn/arbiter.py", line 525, in reap_workers
      raise HaltServer(reason, self.WORKER_BOOT_ERROR)
  gunicorn.errors.HaltServer: &lt;HaltServer 'Worker failed to boot.' 3&gt;
  </code></pre>
  
  <p>Python 37
  Django 2.1.14</p>
  
  <p>I`m first time with Django&amp;GAE, pleese help</p>