test: Replace hashlib.new with named constructor

test/functional/test_framework/messages.py

@@ -64,13 +64,15 @@ FILTER_TYPE_BASIC = 0
 
 WITNESS_SCALE_FACTOR = 4
 
-# Serialization/deserialization tools
+
 def sha256(s):
-    return hashlib.new('sha256', s).digest()
+    return hashlib.sha256(s).digest()
+
 
 def hash256(s):
     return sha256(sha256(s))
 
+
 def ser_compact_size(l):
     r = b""
     if l < 253: