When creating extension installation scripts for the extension testing environment, it can be difficult to analyse where issues are in the script. For example, when we were creating the Semantic MediaWiki installation script we did not know why the setup program was not running correctly. Previously, the installer would not output anything from install files and so no debugging was possible. Now, there is a debug flag which allows us to see detailed information - enabling us to find and fix issues far more efficiently than before.
To use this flag, add "debug=True" to your settings.py file.