gunicorn.errors.HaltServer: <HaltServer 'Worker failed to boot.' 3> django

run guncorn with --preload can see the error log, like this

gunicorn app:application --preload -b 0.0.0.0:5000 

This will usually give you a more detailed error message.

Actually the problem here was the wsgi file itself, previously before django 1.3 the wsgi file was named with an extension of .wsgi, but now in the recent versions it will be created with and extension of .py that is the wsgi file must be a python module

so the file should be hello_wsgi.py and command should be

gunicorn  hello:application -b xx.xxx.xxx.xx:8000

You didn't show a full output. It probably looks like

$ gunicorn elcarweb.wsgi
[2015-10-27 21:01:47 +0000] [5429] [INFO] Starting gunicorn 19.2.1
[2015-10-27 21:01:47 +0000] [5429] [INFO] Listening at: http://127.0.0.1:8000 (5429)
[2015-10-27 21:01:47 +0000] [5429] [INFO] Using worker: sync
[2015-10-27 21:01:47 +0000] [5434] [INFO] Booting worker with pid: 5434
[2015-10-27 21:01:47 +0000] [5434] [ERROR] Exception in worker process:
Traceback (most recent call last):
  File "/home/tomek/Elcar/elcarweb/env/lib/python2.7/site-packages/gunicorn/arbiter.py", line 503, in spawn_worker
    worker.init_process()
  File "/home/tomek/Elcar/elcarweb/env/lib/python2.7/site-packages/gunicorn/workers/base.py", line 116, in init_process
    self.wsgi = self.app.wsgi()
  File "/home/tomek/Elcar/elcarweb/env/lib/python2.7/site-packages/gunicorn/app/base.py", line 67, in wsgi
    self.callable = self.load()
  File "/home/tomek/Elcar/elcarweb/env/lib/python2.7/site-packages/gunicorn/app/wsgiapp.py", line 65, in load
    return self.load_wsgiapp()
  File "/home/tomek/Elcar/elcarweb/env/lib/python2.7/site-packages/gunicorn/app/wsgiapp.py", line 52, in load_wsgiapp
    return util.import_app(self.app_uri)
  File "/home/tomek/Elcar/elcarweb/env/lib/python2.7/site-packages/gunicorn/util.py", line 355, in import_app
    __import__(module)
ImportError: No module named elcarweb.wsgi
Traceback (most recent call last):
  File "/home/tomek/Elcar/elcarweb/env/lib/python2.7/site-packages/gunicorn/arbiter.py", line 503, in spawn_worker
    worker.init_process()
  File "/home/tomek/Elcar/elcarweb/env/lib/python2.7/site-packages/gunicorn/workers/base.py", line 116, in init_process
    self.wsgi = self.app.wsgi()
  File "/home/tomek/Elcar/elcarweb/env/lib/python2.7/site-packages/gunicorn/app/base.py", line 67, in wsgi
    self.callable = self.load()
  File "/home/tomek/Elcar/elcarweb/env/lib/python2.7/site-packages/gunicorn/app/wsgiapp.py", line 65, in load
    return self.load_wsgiapp()
  File "/home/tomek/Elcar/elcarweb/env/lib/python2.7/site-packages/gunicorn/app/wsgiapp.py", line 52, in load_wsgiapp
    return util.import_app(self.app_uri)
  File "/home/tomek/Elcar/elcarweb/env/lib/python2.7/site-packages/gunicorn/util.py", line 355, in import_app
    __import__(module)
ImportError: No module named elcarweb.wsgi
[2015-10-27 21:01:47 +0000] [5434] [INFO] Worker exiting (pid: 5434)
Traceback (most recent call last):
  File "/home/tomek/Elcar/elcarweb/env/bin/gunicorn", line 11, in <module>
    sys.exit(run())
  File "/home/tomek/Elcar/elcarweb/env/lib/python2.7/site-packages/gunicorn/app/wsgiapp.py", line 74, in run
    WSGIApplication("%(prog)s [OPTIONS] [APP_MODULE]").run()
  File "/home/tomek/Elcar/elcarweb/env/lib/python2.7/site-packages/gunicorn/app/base.py", line 189, in run
    super(Application, self).run()
  File "/home/tomek/Elcar/elcarweb/env/lib/python2.7/site-packages/gunicorn/app/base.py", line 72, in run
    Arbiter(self).run()
  File "/home/tomek/Elcar/elcarweb/env/lib/python2.7/site-packages/gunicorn/arbiter.py", line 170, in run
    self.manage_workers()
  File "/home/tomek/Elcar/elcarweb/env/lib/python2.7/site-packages/gunicorn/arbiter.py", line 473, in manage_workers
    self.spawn_workers()
  File "/home/tomek/Elcar/elcarweb/env/lib/python2.7/site-packages/gunicorn/arbiter.py", line 537, in spawn_workers
    time.sleep(0.1 * random.random())
  File "/home/tomek/Elcar/elcarweb/env/lib/python2.7/site-packages/gunicorn/arbiter.py", line 210, in handle_chld
    self.reap_workers()
  File "/home/tomek/Elcar/elcarweb/env/lib/python2.7/site-packages/gunicorn/arbiter.py", line 455, in reap_workers
    raise HaltServer(reason, self.WORKER_BOOT_ERROR)
gunicorn.errors.HaltServer: <HaltServer 'Worker failed to boot.' 3>

Last trackback is almost the same, but before You see required informations:

ImportError: No module named elcarweb.wsgi

If You see this error, then solution is run gunicorn with --chdir=/your/app/dir parameter.