Argument list too long error

[DyegoCosta]

$ vagrant@local:/vagrant/core$ what_to_run rspec
$ /var/lib/gems/2.1.0/gems/what_to_run-1.0.0/lib/what_to_run/runner.rb:17:in `exec': Argument list too long - bundle exec rspec -e <RSpec extensive spec list> (Errno::E2BIG)
    from /var/lib/gems/2.1.0/gems/what_to_run-1.0.0/lib/what_to_run/runner.rb:17:in `run'
    from /var/lib/gems/2.1.0/gems/what_to_run-1.0.0/lib/what_to_run/cli.rb:15:in `run'
    from /var/lib/gems/2.1.0/gems/what_to_run-1.0.0/bin/what_to_run:5:in `<top (required)>'
    from /usr/local/bin/what_to_run:23:in `load'
    from /usr/local/bin/what_to_run:23:in `<main>'