add flake linter, fix linter issues

[totlsota]

I checked out the client and was going to lint it.There was a short journey to get there:

First any poetry action was I was giving a runtime error:

  RuntimeError

  The Poetry configuration is invalid:
    - Additional properties are not allowed ('group' was unexpected)

As reported here, poetry version > 1.2.x is required for certain features. Added comment to README.md.

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Second, the current live poetry install script fails to update and poetry self update fails as per here

remove like this:

curl -sSL https://raw.githubusercontent.com/python-poetry/poetry/master/get-poetry.py | python3 - --uninstall

install like this:

curl -sSL https://install.python-poetry.org | python3 - --git https://github.com/python-poetry/poetry.git@master

check version is > 1.2x poetry --version

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Finally, added the flake8 linter, corrected the linter issues