Added suggestion in helptext for unnecessary-comprehension checker

[yushao2]

Steps

• Add yourself to CONTRIBUTORS if you are a new contributor.
• Add a ChangeLog entry describing what your PR does.
• If it's a new feature or an important bug fix, add a What's New entry in
  doc/whatsnew/<current release.rst>.
• Write a good description on what the PR does.

Description

Improved help text for unnecessary-comprehension -- now provides suggestion of what could be used instead.

E.g:

a_dict = dict()
[(k, v) for k, v in a_dict.items()]  # [unnecessary-comprehension]

Help text:

unnecessary-comprehension:17:0::Unnecessary use of a comprehension, use list(a_dict.items()) instead.

Type of Changes

	Type
✓	📝 Documentation
✓	🔨 Refactoring

Related Issue

Closes #4499

[coveralls]

Coverage increased (+0.002%) to 91.827% when pulling 0912d67 on yushao2:refactoring-4499 into 44eab78 on PyCQA:master.

[Pierre-Sassoulas]

Looks good, maybe we could also advise "use my_list" instead of "use list(my_list) if it's already a set/list/dict ? :) (Yes, I've seen this this in a real code base 😄)

[yushao2]

Looks good, maybe we could also advise "use my_list" instead of "use list(my_list) if it's already a set/list/dict ? :) (Yes, I've seen this this in a real code base )

oops -- my bad. I'll try to incorporate those in

[Pierre-Sassoulas]

Nice work again ! :)

[cdce8p]

Some comments

[cdce8p]

LGTM