devel/py-prospector: Add py-prospector 1.9.0

Prospector is a tool to analyze Python code and output information about errors,
potential problems, convention violations and complexity.

It brings together the functionality of other Python analysis tools such as
Pylint, pycodestyle, and McCabe complexity. See the Supported Tools
documentation section for a complete list.

The primary aim of Prospector is to be useful 'out of the box'. A common
complaint of other Python analysis tools is that it takes a long time to filter
through which errors are relevant or interesting to your own coding style.
Prospector provides some default profiles, which hopefully will provide a good
starting point and will be useful straight away, and adapts the output depending
on the libraries your project uses.