Despite the best efforts in testing, applications often still contain bugs when they're put into production use. A wider variety of browsers will be used, and novice users will often try to do strange things that provoke a Python exception. It's important to detect such exceptions and to record enough information to permit debugging them.
Quixote can automatically e-mail exceptions to a configured address. To enable this, set ERROR_EMAIL in the configuration file you're using:
ERROR_EMAIL = 'email@example.com'
This configuration file is read using the .read_config(filename) method of your Publisher instance.
Enabling e-mailed tracebacks doesn't affect the page returned to the client who's stumbled into an error. To change that, see the HidingExceptions recipe.