Travis fails to execute my script

I just started to work with Travis in order to build and deploy a python-based application on windows. Based on the documentation I could read, I derived the following .travis.yml file:

notifications:
  email: false
jobs:
 include:
 - os: windows
   language: shell
   script:
    - choco install python3
    - choco install nsis
    - .travis/windows_build_app.sh"

and my .travis/windows_build_app.sh file just contains echo ${TRAVIS_BUILD_DIR} for testing purpose.

When pushing and triggering the build, the two choco commands are correctly executed but travis fails with running my script. It ends up with the following error:

$ .travis/windows_build_app.sh"

The command ".travis/windows_build_app.sh"" exited with 1.

Done. Your build exited with 1.

/c/Users/travis/.travis/functions: eval: line 109: unexpected EOF while looking for matching `"'

/c/Users/travis/.travis/functions: eval: line 110: syntax error: unexpected end of file

Would you have any idea about what is wrong with my setup ?

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