Broken pipe error

### CKAN Version if known (or site URL)
2.8.1

### Please describe the expected behaviour
No errors after an valid HTTP request.

### Please describe the actual behaviour
```
ckan | Traceback (most recent call last):
ckan | File "/usr/lib/ckan/venv/local/lib/python2.7/site-packages/paste/httpserver.py", line 1068, in process_request_in_thread
ckan | self.finish_request(request, client_address)
ckan | File "/usr/lib/python2.7/SocketServer.py", line 331, in finish_request
ckan | self.RequestHandlerClass(request, client_address, self)
ckan | File "/usr/lib/python2.7/SocketServer.py", line 654, in __init__
ckan | self.finish()
ckan | File "/usr/lib/python2.7/SocketServer.py", line 713, in finish
ckan | self.wfile.close()
ckan | File "/usr/lib/python2.7/socket.py", line 283, in close
ckan | self.flush()
ckan | File "/usr/lib/python2.7/socket.py", line 307, in flush
ckan | self._sock.sendall(view[write_offset:write_offset+buffer_size])
ckan | error: [Errno 32] Broken pipe
```
Also reported by another user: https://gitter.im/ckan/chat?at=5bc88344ef4afc4f2892f371
This error fills the logs with garbage.

### What steps can be taken to reproduce the issue?
Open few pages.