AssertionError: .accepted_renderer not set on Response
出錯原因，沒有在合法的方法內使用 response 響應，之前在dispatch內直接return 了，導致報錯，return response 必須放在 get post 等方法內。
按道理講，django視圖會先經過dispatch分發，如果我們在分發的時候發現權限問題，那么提前響應應該沒問題，那么為啥會報錯呢？
報錯信息顯示accepted_renderer沒有在Response內設定，找一下源碼，如下(具體原因都在下面代碼后面的注釋里了)：
def dispatch(self, request, *args, **kwargs):
"""
`.dispatch()` is pretty much the same as Django's regular dispatch,
but with extra hooks for startup, finalize, and exception handling.
"""
self.args = args
self.kwargs = kwargs
request = self.initialize_request(request, *args, **kwargs)
self.request = request
self.headers = self.default_response_headers # deprecate?
try:
self.initial(request, *args, **kwargs)
# Get the appropriate handler method
if request.method.lower() in self.http_method_names:
handler = getattr(self, request.method.lower(),
self.http_method_not_allowed)
else:
handler = self.http_method_not_allowed
response = handler(request, *args, **kwargs) # 這里發現了，請求響應是在dispatch方法內部完成的，響應也是dispatch代為返回的，到這里也沒問題，問題在下面。
except Exception as exc:
response = self.handle_exception(exc)
self.response = self.finalize_response(request, response, *args, **kwargs) # 在響應之前，dispatch對視圖方法返回的響應又加工了一次
return self.response
def finalize_response(self, request, response, *args, **kwargs):
"""
Returns the final response object.
"""
# Make the error obvious if a proper response is not returned
assert isinstance(response, HttpResponseBase), (
'Expected a `Response`, `HttpResponse` or `HttpStreamingResponse` '
'to be returned from the view, but received a `%s`'
% type(response)
)
if isinstance(response, Response):
if not getattr(request, 'accepted_renderer', None):
neg = self.perform_content_negotiation(request, force=True)
request.accepted_renderer, request.accepted_media_type = neg
response.accepted_renderer = request.accepted_renderer # 這里，Response 會定義一個屬性 accepted_renderer，也就是說，視圖響應的不僅僅是一個 Response，而是加工過的Response，所以如果在dispatch內直接響應Response，就是跳過了后面加工哪一步，就會報錯。
response.accepted_media_type = request.accepted_media_type
response.renderer_context = self.get_renderer_context()
for key, value in self.headers.items():
response[key] = value
return response
django.core.exceptions.AppRegistryNotReady: Apps aren't loaded yet.
出錯原因，兩個，第一，相關包沒有安裝或者版本有問題；第二，在不合適的地方使用了項目的model模型，版本不同情況不一樣。
XXX doesn't declare an explicit app_label and either isn't in an application in INSTALLED_APPS or else was imported before its application was loaded. This will no longer be supported
出錯原因，在不合適的地方導用了model，如本次是在 app.__init__.py中導入本app的model導致的
虛擬環境中，Python庫的安裝直接使用pip安裝，不用加sudo，不然項目沒有權限使用該庫，會導致出現 Apps aren't loaded yet.