Make y/n validator case insensitive (#5294)

* Make y/n validator case insensitive
* Add changelog entry

Author: tusharsadhwani

ChangeLog

@@ -158,6 +158,8 @@ Release date: TBA
 
   Closes #5208
 
+* Make yn validator case insensitive, to allow for ``True`` and ``False`` in config files.
+
 
 What's New in Pylint 2.11.2?
 ============================

doc/whatsnew/2.12.rst

@@ -156,3 +156,5 @@ Other Changes
   have functioning shared semaphore implementation.
 
   Closes #5216
+
+* Make yn validator case insensitive, to allow for ``True`` and ``False`` in config files.

pylint/config/option.py

@@ -50,6 +50,8 @@ def _choice_validator(choices, name, value):
 def _yn_validator(opt, _, value):
     if isinstance(value, int):
         return bool(value)
+    if isinstance(value, str):
+        value = value.lower()
     if value in ("y", "yes", "true"):
         return True
     if value in ("n", "no", "false"):