This is actually one of the ways in which I'm somewhat skeptical of the Catholic church's doctrine.
I have no doubts that Pope Francis is a very kind, wise, and Godly man, but he's just that: a man. God's Word says "For all have sinned and fall short of the Glory of God" (Romans 3:23), and that includes Pope Francis.
Only one man was born without sin, and that man was Jesus Christ. Pope Francis may be the leader-figure of the Catholic church, but he has every bit the same capacity for fallibility and sin as the rest of us.