transaction: fix an error string with bytestr() on a repr()d value

Fixes test-rollback.t on Python 3.

Differential Revision: https://phab.mercurial-scm.org/D2674

contrib/python3-whitelist

@@ -347,6 +347,7 b' test-revlog-mmapindex.t'
 test-revlog-packentry.t
 test-revset-dirstate-parents.t
 test-revset-outgoing.t
+test-rollback.t
 test-run-tests.py
 test-schemes.t
 test-serve.t

mercurial/transaction.py

@@ -18,6 +18,7 b' import errno'
 from .i18n import _
 from . import (
     error,
+    pycompat,
     util,
 )
 
@@ -604,7 +605,8 b' def rollback(opener, vfsmap, file, repor'
             f, o = l.split('\0')
             entries.append((f, int(o), None))
         except ValueError:
-            report(_("couldn't read journal entry %r!\n") % l)
+            report(
+                _("couldn't read journal entry %r!\n") % pycompat.bytestr(l))
 
     backupjournal = "%s.backupfiles" % file
     if opener.exists(backupjournal):