py3: fix kwargs handling in hgext/absorb.py

This fixes couple of tests on Python 3. There is only one absorb test left
failing on Python 3.

Differential Revision: https://phab.mercurial-scm.org/D4694

contrib/python3-whitelist

@@ -1,7 +1,9 b''
 test-abort-checkin.t
 test-absorb-filefixupstate.py
 test-absorb-phase.t
+test-absorb-rename.t
 test-absorb-strip.t
+test-absorb.t
 test-add.t
 test-addremove-similar.t
 test-addremove.t

hgext/absorb.py

@@ -972,6 +972,7 b' def absorbcmd(ui, repo, *pats, **opts):'
 
     Returns 0 on success, 1 if all chunks were ignored and nothing amended.
     """
+    opts = pycompat.byteskwargs(opts)
     state = absorb(ui, repo, pats=pats, opts=opts)
     if sum(s[0] for s in state.chunkstats.values()) == 0:
         return 1