Save to DB returns false with no error message, how to diagnose it?

Hi. Working along a tutorial, I am trying to create a user for my application, and save it to a User database table. However, when I try to save the user (i.e. add a line to the User table) the Ruby console just returns false, with no explanation. Using create instead of save does the same. I have tried deleting the database and doing the migration again, but got the same result. How can I obtain more diagnostic on why the save to database is failing?
Here a transcript from the console:
Loading development environment (Rails 3.2.9)
irb(main):001:0> user= User.new screen_name: “ginopino”, real_name: “Gino Pilotino”, password: “foobar”, password_confirmation: “foobar”
=> #<User id: nil, screen_name: “ginopino”, real_name: “Gino Pilotino”, created_at: nil, updated_at: nil, password_digest: “$2a$10$T.cnOdhdXPyBt/iQPLGJXuWN62F8FoPgkX9UbXyEWqCh…”>
irb(main):002:0> user.save
←[1m←[36m (0.0ms)←[0m ←[1mbegin transaction←[0m
←[1m←[35m (0.0ms)←[0m rollback transaction
=> false
irb(main):004:0>

Hi. Working along a tutorial, I am trying to create a user for my application, and save it to a User database table. However, when I try to save the user (i.e. add a line to the User table) the Ruby console just returns false, with no explanation. Using create instead of save does the same. I have tried deleting the database and doing the migration again, but got the same result. How can I obtain more diagnostic on why the save to database is failing?

Here a transcript from the console:

Loading development environment (Rails 3.2.9)
irb(main):001:0> user= User.new screen_name: "ginopino", real_name: "Gino Pilotino", password: "foobar", password_confirmation: "foobar"
=> #<User id: nil, screen_name: "ginopino", real_name: "Gino Pilotino", created_at: nil, updated_at: nil, password_digest: "$2a$10$T.cnOdhdXPyBt/iQPLGJXuWN62F8FoPgkX9UbXyEWqCh...">
irb(main):002:0> user.save
  ←[1m←[36m (0.0ms)←[0m ←[1mbegin transaction←[0m
  ←[1m←[35m (0.0ms)←[0m rollback transaction
=> false
irb(main):004:0>

Thank you Craig, that resolved it.
user.errors reminded me that I had imposed a constraint on the password length, and my password did not respect it.