The Juneteenth Film Festival, celebrating the Emancipation and African-American history, opens tonight in the Twin Cities with the first of six films. "Melvin Van Pebbles: Classified X", about the portrayal of blacks in film, will show at the Minnesota History Center at 7 o'clock. A lesser-known bit of African-American history, the rise of black newspapers is the subject of Director Stanley Nelson's film "Soldiers Without Swords: The Black Press." Nelson will present his documentary next Tuesday evening at the Weisman Art Museum. Nelson says even he was surprised at the power of the black press which grew out of a bitter relationship with the mainstream media.