SequenceMatcher(None, [], []).get_grouped_opcodes() now returns a generator
that behaves as if both lists has an empty string in each of them.

Closes bug #979794 (and duplicate bug #980117).
diff --git a/Misc/NEWS b/Misc/NEWS
index 73abaa4..507c7a5 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -29,6 +29,10 @@
 Library
 -------
 
+- Bug #979794: difflib.get_grouped_opcodes() now handles the case of when it is
+  comparing two empty lists.  Was affecting both context_diff() and
+  unified_diff().  Was also a duplicate of bug #980117.
+
 - Bug #980938: smtplib now prints debug output to sys.stderr.
 
 - Bug #930024: posixpath.realpath() now handles infinite loops in symlinks by