When I ran install_master.sh, the final "puppet apply" led to a few errors similar to this:
Error: /Stage[main]/Zuul::Server/File[/etc/zuul/layout]: Could not evaluate: Could not retrieve information from environment production source(s) file:/etc/project-config/zuul
I investigated and found that my /etc/project-config did not contain any of the config files. Instead, it contained the tree of your os-ext-testing repo.
It looks like it's due to a mistake on line 131 of install_master.sh. You've set project_config_repo to $OSEXT_REPO. I think it should be $DATA_PATH. I made that change in my local copy and it seemed to work.