Add a raise for generate_projects if Python is too old (#29432)
Add a raise for generate_projects if Python is too old (#29432)

* Add a raise for generate_projects if Python is too old

* Update the comment

* Resolve the YAPF difference between local 0.30 and kokoro's 0.30

* YAPF
grpc/grpc,vjpai/grpc,grpc/grpc,ejona86/grpc,jtattermusch/grpc,ctiller/grpc,stanley-cheung/grpc,stanley-cheung/grpc,ejona86/grpc,nicolasnoble/grpc,jtattermusch/grpc,vjpai/grpc,vjpai/grpc,ctiller/grpc,ctiller/grpc,nicolasnoble/grpc,ctiller/grpc,ejona86/grpc,stanley-cheung/grpc,grpc/grpc,stanley-cheung/grpc,grpc/grpc,jtattermusch/grpc,nicolasnoble/grpc,grpc/grpc,ejona86/grpc,vjpai/grpc,ejona86/grpc,ctiller/grpc,stanley-cheung/grpc,ejona86/grpc,jtattermusch/grpc,nicolasnoble/grpc,ejona86/grpc,stanley-cheung/grpc,ctiller/grpc,nicolasnoble/grpc,stanley-cheung/grpc,grpc/grpc,grpc/grpc,ejona86/grpc,vjpai/grpc,ctiller/grpc,ejona86/grpc,nicolasnoble/grpc,ejona86/grpc,ctiller/grpc,vjpai/grpc,vjpai/grpc,vjpai/grpc,ejona86/grpc,vjpai/grpc,stanley-cheung/grpc,jtattermusch/grpc,jtattermusch/grpc,nicolasnoble/grpc,grpc/grpc,nicolasnoble/grpc,vjpai/grpc,grpc/grpc,ctiller/grpc,ctiller/grpc,grpc/grpc,nicolasnoble/grpc,jtattermusch/grpc,ctiller/grpc,stanley-cheung/grpc,nicolasnoble/grpc,nicolasnoble/grpc,ejona86/grpc,jtattermusch/grpc,jtattermusch/grpc,stanley-cheung/grpc,stanley-cheung/grpc,ctiller/grpc,grpc/grpc,nicolasnoble/grpc,jtattermusch/grpc,grpc/grpc,vjpai/grpc,jtattermusch/grpc,stanley-cheung/grpc,vjpai/grpc,jtattermusch/grpc