Just started using mpw7a. By default it sets sky130B. Got the warning as shown in the picture. However, the flow completes. Hope this is fine.

Unfortunately, there are 2 cvc programs. OSS CVC verilog http://www.tachyon-da.com/ and CVC-RV (Reliability verfication) which I maintain here https://github.com/d-m-bailey/cvc. One of the drawbacks of TLAs (three-letter acronymns). This message probably refers to CVC-RV, which was never fully implemented in the design flow. If you want, you can run CVC-RV on your top level design using https://github.com/d-m-bailey/sconnect_for_sky130_magic