sysdata/mem: use py3.format_units
sysdata/mem: use py3.format_units

ultrabug/py3status,Andrwe/py3status,tobes/py3status,valdur55/py3status,guiniol/py3status,ultrabug/py3status,ultrabug/py3status,tobes/py3status,valdur55/py3status,guiniol/py3status,Andrwe/py3status,valdur55/py3status