Updated doctest output for Python 3.6

examples.py

@@ -11,7 +11,7 @@ def parse(pair):
     >>> parse('invalid')
     Traceback (most recent call last):
       ...
-    ValueError: need more than 1 value to unpack
+    ValueError: not enough values to unpack (expected 2, got 1)
 
     Likewise if there is more than one separator:
     >>> parse('first: second: third')