From 018da184124870d21ff5608c7b09b33a369bd9df Mon Sep 17 00:00:00 2001
From: iceboy <me@iceboy.org>
Date: Sun, 29 Oct 2017 13:23:20 -0700
Subject: [PATCH] Fixes #379

---
 vj4/handler/base.py | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/vj4/handler/base.py b/vj4/handler/base.py
index 6f4cfed7..987fe5f1 100644
--- a/vj4/handler/base.py
+++ b/vj4/handler/base.py
@@ -270,7 +270,14 @@ async def binary(self, data, content_type='application/octet-stream', file_name=
 
   @property
   def prefer_json(self):
-    for d in accept.parse(self.request.headers.get('Accept')):
+    accept_header = self.request.headers.get('Accept')
+    try:
+      parse_result = accept.parse(accept_header)
+    except (ValueError, IndexError):
+      # the accept library throws bogus exceptions
+      _logger.warning('Unparsable accept header: %s', accept_header)
+      return False
+    for d in parse_result:
       if d.media_type == 'application/json':
         return True
       elif d.media_type == 'text/html' or d.all_types: