Why are A-List celebs already raving about Bradley Cooper's upcoming "A Star Is Born"

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There seemed to have been a few private screenings of Bradley Cooper‘s upcoming remake of  "A Star Is Born" (only due for release in October). Three major celebs are already raving about it, trying to kickstart an Oscar campaign via word of mouth. Barbra Streisand, Sean Penn, and Robert De Niro — have spoken highly of it.
Streisand: “Oh, I can’t say too much…I haven’t seen too much, but it’s good…it’s very, very good.” Penn: “One of the most beautiful, fantastic, it’s the best, and most importantly commercial film I have seen in so many years” De Niro: “It’s terrific and Bradley is excellent in it…the movie is wonderful…I hope it gets the attention I feel it should when it opens…Bradley learned to sing…he really worked hard and it paid off…you see all the hard work he did, it’s special.”
What is really going on here? Do we have the second coming of Bob Fosse being released this October? Or is this just friends helping a friend? We have no trailer whatsoever, I, in fact, couldn't care less for the film on paper for, but this advanced buzz has surely piqued my interest.

The official synopsis reads "A movie star helps a young singer and actress find fame, even as age and alcoholism send his own career into a downward spiral." Cooper writes, directs and stars. The film also includes Lady Gaga, Sam Elliot, and Dave Chappelle.