Issue #2478: Decimal(sqrt(0)) failed when the decimal context
was not explicitly supplied.
diff --git a/Misc/NEWS b/Misc/NEWS
index 4afd6ca..65815f7 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -72,6 +72,8 @@
 Library
 -------
 
+- Issue #2478: fix failure of decimal.Decimal(0).sqrt()
+
 - Issue #2432: give DictReader the dialect and line_num attributes
   advertised in the docs.