Fix python linter errors

[Yury-Fridlyand]

Describe the feature

flake8 reports a lot of errors, but all of them ignored in CI. It is suppressed by --exit-zero flag.
We need to resolve all errors reported and update CI.

Use Case

-

Proposed Solution

No response

Other Information

No response

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

Client version used

1.1

Environment details (OS name and version, etc.)

N/A