bpo-29723: Add missing NEWS entry (#638)

Author: ncoghlan

Misc/NEWS

@@ -10,6 +10,14 @@ What's New in Python 3.7.0 alpha 1?
 Core and Builtins
 -----------------
 
+- bpo-29723: The ``sys.path[0]`` initialization change for bpo-29139 caused a
+ regression by revealing an inconsistency in how sys.path is initialized when
+ executing ``__main__`` from a zipfile, directory, or other import location.
+ The interpreter now consistently avoids ever adding the import location's
+ parent directory to ``sys.path``, and ensures no other ``sys.path`` entries
+ are inadvertently modified when inserting the import location named on the
+ command line.
+
 - bpo-29568: Escaped percent "%%" in the format string for classic string
  formatting no longer allows any characters between two percents.