Fix 4227: Black does not print errors with --quiet --check

CHANGES.md

@@ -44,6 +44,7 @@
 
 ### Documentation
 
+- Note what happens when --check is called with --quiet (#4236)
 <!-- Major changes to documentation and policies. Small docs changes
      don't need a changelog entry. -->
 

docs/usage_and_configuration/the_basics.md

@@ -183,6 +183,9 @@ Don't write the files back, just return the status. _Black_ will exit with:
 - code 1 if some files would be reformatted; or
 - code 123 if there was an internal error
 
+If used in combination with `--quiet` then only the exit code will be returned, unless
+there was an internal error.
+
 ```console
 $ black test.py --check
 All done! ✨ 🍰 ✨