The error message can't be returned to client when HTTPUnprocessableEntity happens

[Haiwei Xu]

When HTTPUnprocessableEntity happens, error messages are not passed to the parameter, so the client can't receive the details of the exception, but just gets the default error message defined in the HTTPUnprocessableEntity class.

 873 class HTTPUnprocessableEntity(HTTPClientError):
 874 """
 875 subclass of :class:`~HTTPClientError`
 876
 877 This indicates that the server is unable to process the contained
 878 instructions. Only for WebDAV.
 879
 880 code: 422, title: Unprocessable Entity
 881 """
 882 ## Note: from WebDAV
 883 code = 422
 884 title = 'Unprocessable Entity'
 885 explanation = 'Unable to process the contained instructions'

That's not good, the error messages should be returned to the client.

[Allison Randal (allison)]

Thanks for the report. Could you provide some more details on the context where this error occurred?