Content-Type of response not correct when Accept is wildcard

[dbaynard]

$> curl -v 127.0.0.1:8000/api/users/nothere

*   Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to 127.0.0.1 (127.0.0.1) port 8000 (#0)
> GET /api/users/nothere HTTP/1.1
> Host: 127.0.0.1:8000
> User-Agent: curl/7.61.1
> Accept: */*
>
< HTTP/1.1 404 Not Found
< Transfer-Encoding: chunked
< Date: Fri, 16 Nov 2018 15:05:23 GMT
< Server: Warp/3.2.25
< Content-Type: */*
<
* Connection #0 to host 127.0.0.1 left intact
UserNotFound% 

The response should have a header with an explicit Content-Type, e.g. Content-Type: text/plain