Apply latest Black to the repository

[BarisSari]

We don't specify the Black version in our requirements_dev.txt, and it has a new version that was released at the end of August (https://black.readthedocs.io/en/stable/change_log.html#b1). Therefore, Travis CI Build failed because there some changes (psf/black#1612). This PR makes this repository compatible with the latest Black version. It also solves flake8 warnings that occurred during the change.

I also updated pre-commit hook. Otherwise, it could try to revert all these changes. The following commands should upgrade the libraries of pre-commit hook:

pre-commit uninstall
pre-commit clean
pre-commit install

[codecov]

Codecov Report

Merging #573 into develop will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop     #573   +/-   ##
========================================
  Coverage    98.94%   98.94%           
========================================
  Files           64       64           
  Lines         5955     5955           
========================================
  Hits          5892     5892           
  Misses          63       63           

Impacted Files	Coverage Δ
importers/e_trac_importer.py	100.00% <ø> (ø)
importers/nisida_importer.py	100.00% <ø> (ø)
importers/replay_contact_importer.py	100.00% <ø> (ø)
importers/replay_importer.py	100.00% <ø> (ø)
pepys_admin/merge.py	99.64% <ø> (ø)
pepys_import/cli.py	100.00% <ø> (ø)
pepys_import/core/formats/rep_line.py	100.00% <ø> (ø)
pepys_import/core/store/sqlite_db.py	100.00% <ø> (ø)
pepys_import/core/validators/enhanced_validator.py	100.00% <ø> (ø)
pepys_import/file/file_processor.py	99.56% <ø> (ø)
... and 6 more

---

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[IanMayo]

A huge piece of work @BarisSari

Thanks.

[robintw]

Looks good, thanks.