py3: fix kwargs handling in hgext/split.py

py3: fix kwargs handling in hgext/split.py

Differential Revision: https://phab.mercurial-scm.org/D3593

--- a/hgext/split.py	Sat May 19 18:24:36 2018 +0530
+++ b/hgext/split.py	Sat May 19 18:25:18 2018 +0530
@@ -60,6 +60,7 @@
     By default, rebase connected non-obsoleted descendants onto the new
     changeset. Use --no-rebase to avoid the rebase.
     """
+    opts = pycompat.byteskwargs(opts)
     revlist = []
     if opts.get('rev'):
         revlist.append(opts.get('rev'))