chore(style): Black style fixes

[JuanjoSalvador]

• Style check and corrections according to Black guidelines, improve.
• Fix linting issues found.

Remain issue needs a huge refactor on some functions and tests. Work in progress.

➜  zerasul-blask git:(fix/black-style) ✗ pipenv run linter
************* Module blask.blogrenderer
blask/blogrenderer.py:76:12: W0707: Consider explicitly re-raising using 'except NotFound as exc' and 'raise page_not_exist_exception from exc' (raise-missing-from)
blask/blogrenderer.py:86:12: W0707: Consider explicitly re-raising using 'except FileNotFoundError as exc' and 'raise page_not_exist_exception from exc' (raise-missing-from)

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Your code has been rated at 9.93/10 (previous run: 9.40/10, +0.53)