From 5bb7db2d6f939ba0626eb606102f478a4e613647 Mon Sep 17 00:00:00 2001
From: Keith Bussell <kbussell@gmail.com>
Date: Fri, 3 Aug 2018 12:42:38 -0700
Subject: [PATCH] Always pass a valid rounding value

Fixes #6015

Prevent an exception in `quantize()` when monkey-patching the decimal
library as cdecimal in Python 2 environments by always passing a valid
(not None) `rounding` value to `quantize()`.
---
 rest_framework/fields.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/rest_framework/fields.py b/rest_framework/fields.py
index 3278cf51c..d5071a1aa 100644
--- a/rest_framework/fields.py
+++ b/rest_framework/fields.py
@@ -1135,11 +1135,12 @@ class DecimalField(Field):
             return value
 
         context = decimal.getcontext().copy()
+        rounding = context.rounding if self.rounding is None else self.rounding
         if self.max_digits is not None:
             context.prec = self.max_digits
         return value.quantize(
             decimal.Decimal('.1') ** self.decimal_places,
-            rounding=self.rounding,
+            rounding=rounding,
             context=context
         )