Black would now echo the location that it determined as the root path
for the project if `--verbose` is enabled by the user, according to
which it chooses the SRC paths, i.e. the absolute path of the project
is `{root}/{src}`.

Closes psf#1880

…a class var in Report

…erbose

This has been done by getting root early and caching it in ctx.obj

For invalid source, log it with colour red when displaying the SRCs log else keep it to the default blue colour. This is done to handle permission related errors and out of tree exceptions gracefully