As per https://docs.python.org/3.11/reference/lexical_analysis.html#encoding-declarations, the default encoding of Python files is UTF-8. In fact, it's been the default encoding since Python 3.0 (released in 2008).
Taskwarrior uses "expire" to refer to deletion of tasks past their "until" date, so let's use `purge` to link this semantically to the `task purge` command.
Co-authored-by: ryneeverett <ryneeverett@gmail.com>