Donatism is the heresy that sacraments must be performed by a priest in a state of grace and with the right intent in order to be effective – in error because it denies the power of God to convey grace to the believing recipient even if the clergy in question has screwed up.
FWIW, Abby, “in a state of sin” is a technical term in Catholicism – although we are all sinners, our sins are forgiven on repentance. According to RCC doctrine, one is “in a state of sin” when one has committed a sin and not yet confessed it and received absolution from a priest in token of God’s forgiveness of the sin, when one returns to “a state of grace.” (Actually, I’m summarizing RCC theology about sin and forgiveness drastically and with consequent error, but as a quick-and-dirty summary, I believe it’s on target.)