Add specs to test where error messages are printed.
user
```ruby
require File.expand_path('../../spec_helper', __FILE__)

describe "The error message caused by an exception" do
  it "is not printed to stdout" do
    out = ruby_exe("this_does_not_exist", :args => "2> /dev/null")
    out.chomp.empty?.should == true

    out = ruby_exe("end #syntax error", :args => "2> /dev/null")
    out.chomp.empty?.should == true
  end
end
```
assistant