Fix #6176: Clear error message when EDITOR not set

[MatMacinf]

Description

Fixes #6176.

(...)

To Do

• [ x] Documentation. (If you've added a new command-line flag, for example, find the appropriate page under docs/ to describe it.)
• [x ] Changelog. (Add an entry to docs/changelog.rst to the bottom of one of the lists near the top of the document.)
• [x ] Tests. (Very much encouraged but not strictly required.)

Changed one line to ensure expected behavior as mentioned in the issue, now beet config -e will have info message when no text editor is available.

[MatMacinf]

All testing was done on docker image without vi or any other text editor, please let me know if more test is required.

[codecov]

Codecov Report

❌ Patch coverage is 40.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.33%. Comparing base (50684b7) to head (65d04f4).
⚠️ Report is 6 commits behind head on master.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
beets/ui/commands/config.py	40.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6311      +/-   ##
==========================================
- Coverage   69.33%   69.33%   -0.01%     
==========================================
  Files         141      141              
  Lines       18793    18794       +1     
  Branches     3061     3061              
==========================================
  Hits        13031    13031              
- Misses       5117     5118       +1     
  Partials      645      645              

Files with missing lines	Coverage Δ
beets/ui/commands/config.py	73.80% <40.00%> (-1.81%)	⬇️

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[westclox-star]

Nice! just installed today and ran into this confusing error.

[snejus]

Merged master into this and moved the changelog note under the Unreleased section. Thanks!

Edit: also fixed the line too long lint issue.