what was the problem ?

The problem was: When I executed

 $ bundle exec rake db:create

I get the next error
.....
ExecJS::RuntimeUnavailable: Could not find a JavaScript runtime. See https://github.com/rails/execjs for a list of available runtimes.
.....
I added

 gem 'execjs'
 gem 'therubyracer', :platforms => :ruby

In the Gemfile and works for me....

i think only include therubyracer gem is enough. No need execjs