This assumes you've got docker-machine installed, running, and can do docker run
docker run --name travis-debug -dit quay.io/travisci/travis-ruby /sbin/init
docker exec -it travis-debug bash -l
rvm install 2.2.5
rvm use 2.2.5
gem install travis
travis version # generates ~/.travis
cd builds
git clone https://github.com/travis-ci/travis-build.git
cd travis-build
ln -s `pwd` ~/.travis/travis-build
bundle install
github_user_name=YOUR_GITHUB_USER_NAME
github_repo=YOUR_GITHUB_REPO
cd ~/builds
mkdir $github_user_name
cd $github_user_name
git clone https://github.com/${github_user_name}/${github_repo}.git
cd $github_repo
# change to the branch or commit you want to investigate
travis compile > ~/builds/ci.sh
cd ~/builds
# You most likely will need to edit ci.sh as it ignores matrix and env
bash ci.sh