Perhaps the script is not asking because it’s already in your app.yml and then gives the error due to this (because the email is already wrong in the file app.yml).
Try changing the email in the file manually and see if it works (nano containers/app.yml).
The line that gave the error tests to see if the Let’s Encrypt email is not empty to show it to you and ask if you want to change it, but because the condition doesn’t wrap the variable in double quotes, the value that is in your app.yml is expanded and give the error of Too many arguments.
I think that if the discourse team wrapped the variable in double quotes would help to avoid cases like those, but they should be rare anyway (probably the 1st time you run the setup, the value was set incorrectly).