Checklist

• I have verified that that issue exists against the master branch of Django REST framework.
• I have searched for similar issues in both open and closed tickets and cannot find a duplicate.
• This is not a usage question. (Those should be directed to the discussion group instead.)
• This cannot be dealt with as a third party library. (We prefer new functionality to be in the form of third party libraries where possible.)
• I have reduced the issue to the simplest possible case.
• I have included a failing test as a pull request. (If you are unable to do so we can still accept the issue.)

Steps to reproduce

• Create any DRF view
• Add a middleware or a signal handler that uses request.POST

Expected behavior

• request.POST works fine

Actual behavior

• AttributeError is raised by Django's HttpRequest._load_post_or_files

The reason the exception is raised is because Django's WSGIReqeust.POST checks if hasattr(self, '_post') (which it doesn't have) and proceeds to _load_post_and_data, which in turn calls parse_file_upload which tries to set self.upload_handlers, but the upload_handler.setter checks if hasattr(self, '_files'). At this point, _files has already been set by DRF (to make closing file handles possible), so it raises an exception.

I think the solution to this is to set request._post in addition to request._files to preserve the interface. I am not sure if there's an easy way to set it to the original POST as it seems DRF only calls _load_data_and_files, which deserializes the data etc.

edited for formatting (@rpkilby)