debuginstall: use %d instead of %s for formatting an int % formatting on bytes on Python 3 is pickier about which % character we specify.

py3: test to check which commands run This test helps us to keep track on the commands which runs to Python 3. The full traceback is hidden. Thanks to Augie and Martijn to wrap it up in four lines.

bisect: build a displayer only once There is multiple spot using this, building it early will help to extract more of the logic into the bisect module.