py3: use '%d' for integers rather than '%s'

obsolete._readmarkers() returns an integer version number.

Differential Revision: https://phab.mercurial-scm.org/D1537

mercurial/debugcommands.py

@@ -296,7 +296,7 b' def _debugobsmarkers(ui, part, indent=0,'
         msg %= indent_string, exc.version, len(data)
         ui.write(msg)
     else:
-        msg = "%sversion: %s (%d bytes)\n"
+        msg = "%sversion: %d (%d bytes)\n"
         msg %= indent_string, version, len(data)
         ui.write(msg)
         fm = ui.formatter('debugobsolete', opts)