I am in the process of installing SageMath version 9.0 (Release Date: 2020-01-01), on a Mac, running Catalina Version 10.15.3, via dmg. When I run sage, I get the message
“python3.7” cannot be opened because the developer cannot be verified.
I cannot progress past this point. (The usual tricks, like "hold option when opening a program", do not work here, since I am running Sage from a terminal.)