Katy Perry delays tour, announces opening acts

- Katy's Witness tour was supposed to start Sept. 7, but will now start Sept. 19
- She says: "Due to unavoidable production delays, major elements of my tour stage design could not be available for me to rehearse on until this week"
- She also announced Noah Cyrus, Purity Ring, and Carly Rae Jepsen will be her opening acts