histedit: fix silly bug that was unpacking a bytestr before writing it

I have this foggy notion that popbuffer() might have returned a list
in the past, but it doesn't anymore, and this was breaking on Python
3. As a bonus, it's probably a ton faster on Python 2 now.

Differential Revision: https://phab.mercurial-scm.org/D2243

hgext/histedit.py

@@ -491,7 +491,7 b' class histeditaction(object):'
         repo.dirstate.setbranch(rulectx.branch())
         if stats and stats[3] > 0:
             buf = repo.ui.popbuffer()
-            repo.ui.write(*buf)
+            repo.ui.write(buf)
             raise error.InterventionRequired(
                 _('Fix up the change (%s %s)') %
                 (self.verb, node.short(self.node)),