py3: preserve chunks as an iterable of bytes

patch.diffstat() returns a bytes. util.chunkbuffer() expects an
iterable of bytes. Feeding it a single bytes instance on Python 3
will iterate the characters as integers. This blows up
util.chunkbuffer.

Differential Revision: https://phab.mercurial-scm.org/D2162

mercurial/logcmdutil.py

@@ -81,7 +81,7 b' def diffordiffstat(ui, repo, diffopts, n'
     if fp is not None or ui.canwritewithoutlabels():
         out = fp or ui
         if stat:
-            chunks = patch.diffstat(util.iterlines(chunks), width=width)
+            chunks = [patch.diffstat(util.iterlines(chunks), width=width)]
         for chunk in util.filechunkiter(util.chunkbuffer(chunks)):
             out.write(chunk)
     else: