nmci: fix importing and flakes warnings

Import manipulation via sys.modules[__name__] = _OBJ() breaks jedi autocompletion. Creating objects in nmci/__init__.py works well and does autocomplete works fine.

Fixed warnings:

• bare excepts (replaced by except Exception)
• unused import/variable (deleted)

Not fixed warnings:

• high cyclomatic complexity
• long lines
• black formats list range with spaces (ex: my_list[1 : index2 - 7]) which flakes does not like

Autocomplete seems to work well with this change:

@RunTests:*