BATON ROUGE — A Donaldsonville man was sentenced to 36 months in federal prison for failing to register as a sex offender, according to federal prosecutors.Patrick Sullivan, 32, also will serve five years of supervised release after his prison term. He was arrested in Donaldsonville on Aug. 25, 2025.In his guilty plea, Sullivan admitted he traveled to Baton Rouge in 2024 and later to Donaldsonville, where he established residency and domicile in…