FORT WORTH, Texas — A former Keller police sergeant pleaded guilty Thursday to illegally pepper-spraying and arresting a man who filmed his son’s interactions with Keller police in August 2020. Blake Shimanek entered the plea on a charge to official oppression, a Class A misdemeanor. With this plea, Shimanek was admitted to the Public Safety Employee Treatment Court, which is a diversion program run by Judge Charles Vanover, who presides over County Criminal Court 8. The diversion program can last anywhere from nine months to two years. The incident occurred Aug. 15, 2020, during the arrest of…