HOLLYWOOD — Warner Bros. Pictures has bought an untitled comedy pitch from writing partners Steve List and Astrid Neal for Mosaic Media to produce in association with Bruce Nash Entertainment.Producers are Mosaic’s Charles Roven and Alex Gartner, with reality TV veteran Bruce Nash and Bob Kosberg exec producing. Among its many projects set up at various studios, Mosaic is producing “Idlewild” for HBO Films. Untitled Warners comedy marks Nash’s continued foray into features after partnering with Kosberg. Concept was hatched by Nash and Kosberg, with List developing it into a story pitch. Nash and Kosberg then went to Mosaic before pitching Warners together. List and Neal have several other projects around town, including “Born to Shop” at 20th Century Fox.