Unpredictable behaviour of travis

I have this error:

dpl.1
Installing deploy dependencies
!!! Script support is experimental !!!
dpl.2
Preparing deploy
dpl.3
Deploying application
/home/travis/.rvm/gems/ruby-2.2.6/gems/dpl-1.8.43/lib/dpl/cli.rb:54:in `system': no implicit conversion of nil into String (TypeError)
    from /home/travis/.rvm/gems/ruby-2.2.6/gems/dpl-1.8.43/lib/dpl/cli.rb:54:in `shell'
    from /home/travis/.rvm/gems/ruby-2.2.6/gems/dpl-1.8.43/lib/dpl/provider/script.rb:18:in `push_app'
    from /home/travis/.rvm/gems/ruby-2.2.6/gems/dpl-1.8.43/lib/dpl/provider.rb:154:in `block in deploy'
    from /home/travis/.rvm/gems/ruby-2.2.6/gems/dpl-1.8.43/lib/dpl/cli.rb:41:in `fold'
    from /home/travis/.rvm/gems/ruby-2.2.6/gems/dpl-1.8.43/lib/dpl/provider.rb:154:in `deploy'
    from /home/travis/.rvm/gems/ruby-2.2.6/gems/dpl-1.8.43/lib/dpl/cli.rb:32:in `run'
    from /home/travis/.rvm/gems/ruby-2.2.6/gems/dpl-1.8.43/lib/dpl/cli.rb:7:in `run'
    from /home/travis/.rvm/gems/ruby-2.2.6/gems/dpl-1.8.43/bin/dpl:5:in `<top (required)>'
    from /home/travis/.rvm/gems/ruby-2.2.6/bin/dpl:23:in `load'
    from /home/travis/.rvm/gems/ruby-2.2.6/bin/dpl:23:in `<main>'
failed to deploy

in the my travis deploy stage

Does anybody know how to fix that?

My travis.yml example:

language: java

jdk:
- oraclejdk8

os:
- linux

branches:
  only:
  - master
  - develop
  - test

before_install:
- curl -fsSL https://clis.ng.bluemix.net/install/linux | sh

install: true
script:
- "./gradlew test -s"

deploy:
  provider: script
  skip_cleanup: true
  scirpt: deploy.sh
  on:
    branch: develop

I don't think that's travis realy execute my deploy script. I think I did something wrong.

But travis lint says that it looks valid