gh-111276: Clarify docs and comments about the role of LC_CTYPE (#111319)

Fix locale.LC_CTYPE documentation to no longer mention string.lower() et al. Those functions were removed in Python 3.0:
https://docs.python.org/2/library/string.html#deprecated-string-functions

Also, fix a comment in logging about locale-specific behavior of `str.lower()`.

Co-authored-by: Hugo van Kemenade <hugovk@users.noreply.github.com>

1 files changed, 10 insertions, 5 deletions

diff --git a/Doc/library/locale.rst b/Doc/library/locale.rst
index 865969e..0d48892 100644
--- a/Doc/library/locale.rst
+++ b/Doc/library/locale.rst
@@ -454,11 +454,16 @@ The :mod:`locale` module defines the following exception and functions:
 
 .. data:: LC_CTYPE
 
-   .. index:: pair: module; string
-
-   Locale category for the character type functions.  Depending on the settings of
-   this category, the functions of module :mod:`string` dealing with case change
-   their behaviour.
+   Locale category for the character type functions.  Most importantly, this
+   category defines the text encoding, i.e. how bytes are interpreted as
+   Unicode codepoints.  See :pep:`538` and :pep:`540` for how this variable
+   might be automatically coerced to ``C.UTF-8`` to avoid issues created by
+   invalid settings in containers or incompatible settings passed over remote
+   SSH connections.
+
+   Python doesn't internally use locale-dependent character transformation functions
+   from ``ctype.h``. Instead, an internal ``pyctype.h`` provides locale-independent
+   equivalents like :c:macro:`!Py_TOLOWER`.
 
 
 .. data:: LC_COLLATE