This is occuring because the application you created is not verified by google so you are not able to login in that you need to verify it by google suite and then you are able to login I also get that problem when i tried to create an browser for myself
I have created project and even i have client_secret.js file, when i try to run the program first time it asks to login, when I tried to login through gmail (which I have used to create project) it says

"Google hasn’t verified this app"

Message, so for that i'm looking how to get out from this step.
How to read files from Google drive through python when it says Google hasn’t verified this app?