Disable warnings related to the use of assert in the tests directory as reported with lint-vetting

[cidrblock]

This adds a few additional files to the per-file-ignore list within the flake8 configuration with an exemption for S101 which is reported by flake8-bandit as part of the wemake style guide which is being vetted.

The list was also alphabetized to ensure new entries were placed in a sane location.

A note was added to the top of the flake8 per-file-ignores indicating that the glob for the tests folder ignoring s101 can be added later. Currently there is a conflict between globs and per-file entries. See PyCQA/flake8#670

This eliminates the S101 entry from the output of tox -e lint-vetting so users of it can see messages only related to the changes they are making and not for files that were previously added to the repository:

1     C812 missing trailing comma
1     RST304 Unknown interpreted text role "mod".
- 13    S101 Use of assert detected. The enclosed code will be removed when compiling to optimised byte code.
1     S404 Consider possible security implications associated with the subprocess module.
1     S603 subprocess call - check for execution of untrusted input.
2     S604 Function call with shell=True parameter identified, possible security issue.
2     WPS111 Found too short name: p < 2
2     WPS115 Found upper-case constant in a class: KEGEX
3     WPS201 Found module with too many imports: 13 > 12
6     WPS210 Found too many local variables: 6 > 5
3     WPS220 Found too deep nesting: 24 > 20
2     WPS221 Found line with high Jones Complexity: 16 > 14
3     WPS226 Found string literal over-use: test_option > 3
9     WPS305 Found `f` string
1     WPS316 Found context manager with too many assignments
6     WPS317 Found incorrect multi-line parameters
2     WPS323 Found `%` string formatting
4     WPS324 Found inconsistent `return` statement
2     WPS414 Found incorrect unpacking target
1     WPS430 Found nested function: getcwd
14    WPS436 Found protected module import: _curses
3     WPS450 Found protected object import: _CursesWindow
1     WPS602 Found using `@staticmethod`

Related #713

[webknjaz]

@cidrblock FYI in diffs there's usually some indentation in the unchanged lines.
It's (like in typical diff output)

  unchanged
- dropped
+ added
  lines

vs (your version)

unchanged
- dropped
+ added
lines

The idea is that all the text content has the same starting point and is aligned accordingly.
I know that it's inconvenient to do in GH comment inputs so I often produce such diffs externally to make it easier. It's possible to do by creating two text files before and after and feeding them to the diff like diff -u before after. Alternatively, text editors like Vim allow producing block indents. So I add two spaces to all the lines like this and then replace some of the spaces with -/+ and duplicate them where necessary.

[ansible-zuul]

LGTM!