获取Facebook图片时芹菜任务错误

我有以下芹菜任务：

@task
def get_users_facebook_as_profile_icon(user_id, facebook_id):
    logger.info('Grabbing users facebook picture')
    url = "http://graph.facebook.com/%s/picture?type=large" % facebook_id

    import requests
    response = requests.get(url)
    if response.status_code != 200:
        raise Exception("Could not get facebook profile picture")
...

在此之后，我还有更多东西，但我不断收到以下错误消息：

"AssertionError('PID check failed. RNG must be re-initialized after fork(). Hint: Try Random.atfork()',)" 


Task was called with args: (3246, 17500596) kwargs: {}. 

The contents of the full traceback was: 

Traceback (most recent call last): 
File "/usr/local/lib/python2.7/dist-packages/celery/app/trace.py", line 240, in trace_task 
R = retval = fun(*args, **kwargs) 
File "/usr/local/lib/python2.7/dist-packages/celery/app/trace.py", line 437, in __protected_call__ 
return self.run(*args, **kwargs) 
File "/home/ubuntu/mounzawebsite/mounza/celery_tasks/login_registration.py", line 42, in get_users_facebook_as_profile_icon 
hashname = user.generate_picture_name() 
File "/home/ubuntu/mounzawebsite/mounza/web/models.py", line 515, in generate_picture_name 
return generate_random_name(None) 
File "/home/ubuntu/mounzawebsite/mounza/web/models.py", line 40, in generate_random_name 
str(random.randint(1, 99982098098908237)) + 
File "/usr/lib/python2.7/dist-packages/Crypto/Random/__init__.py", line 41, in get_random_bytes 
return _UserFriendlyRNG.get_random_bytes(n) 
File "/usr/lib/python2.7/dist-packages/Crypto/Random/_UserFriendlyRNG.py", line 213, in get_random_bytes 
return _get_singleton().read(n) 
File "/usr/lib/python2.7/dist-packages/Crypto/Random/_UserFriendlyRNG.py", line 163, in read 
return _UserFriendlyRNG.read(self, bytes) 
File "/usr/lib/python2.7/dist-packages/Crypto/Random/_UserFriendlyRNG.py", line 122, in read 
self._check_pid() 
File "/usr/lib/python2.7/dist-packages/Crypto/Random/_UserFriendlyRNG.py", line 138, in _check_pid 
raise AssertionError("PID check failed. RNG must be re-initialized after fork(). Hint: Try Random.atfork()") 
AssertionError: PID check failed. RNG must be re-initialized after fork(). Hint: Try Random.atfork() 

我尝试在网上进行深入研究，但找不到根本原因。但这是发生此错误的唯一任务。唯一的区别是我正在从Facebook下载图像，但在其他任何地方都看不到此问题，包括我下载图像的其他任务。

如果通过Web浏览器进行操作，则URL可以完美运行，但是仅通过此任务它会失败。还有其他可能导致这种情况的因素吗？

我已经竭尽全力解决这个问题:(