Use the pure python io module to avoid some interaction between gunicorn, wsgi, and bufferedreader that prevents gunicorn from properly sending the files.

data/userfiles.py

@@ -5,7 +5,7 @@ import magic
 from uuid import uuid4
 from flask import url_for, request, send_file, make_response, abort
 from flask.views import View
-from io import BufferedReader
+from _pyio import BufferedReader
 
 
 logger = logging.getLogger(__name__)

storage/cloud.py

@@ -7,7 +7,7 @@ import boto.gs.connection
 import boto.s3.key
 import boto.gs.key
 
-from io import UnsupportedOperation, BufferedIOBase
+from io import BufferedIOBase
 
 from storage.basestorage import BaseStorage
 
@@ -18,15 +18,12 @@ logger = logging.getLogger(__name__)
 class StreamReadKeyAsFile(BufferedIOBase):
   def __init__(self, key):
     self._key = key
-    self._finished = False
 
   def read(self, amt=None):
-    if self._finished:
+    if self.closed:
       return None
 
     resp = self._key.read(amt)
-    if not resp:
-      self._finished = True
     return resp
 
   def readable(self):