Execute flake8 with fiasko_bro

[Melevir]

if VALIDATOR_SETTINGS['is_user_flake8'] == True (default is true), then execute flake8 validation on path with path to setup.cfg if exists.
Errors from flake8 should be if form of ('flake8: E221', 'for example, ...') (error type with prefix and no comment) and should be grouped per error type (one line per error).

[vergeev]

I think I'm going to use flake's Python API. But: Flake8 3.0.0 presently does not have a public, stable Python API. according to this.

More specificly, I'm trying to make use of the legacy API.

[vergeev]

As I described in the Slack chat, this may not be possible to accomplish in a clean way.

It seems to me our choices are:

• use internal classes and methods of flake8 in order to retrieve the information we need;
• run flake8 with something like fabric and parse the output.

Since I don't like either of those, I am proposing to close the issue.