[5.1.x] Fixed #35627 -- Raised a LookupError rather than an unhandled ValueError in get_supported_language_variant().

LocaleMiddleware didn't handle the ValueError raised by
get_supported_language_variant() when language codes were
over 500 characters.

Regression in 9e9792228a.

Backport of 0e94f292cd from main.

docs/ref/utils.txt

@@ -1108,7 +1108,7 @@ For a complete discussion on the usage of the following see the
     ``'es-ar'`` isn't.
 
     ``lang_code`` has a maximum accepted length of 500 characters. A
-    :exc:`ValueError` is raised if ``lang_code`` exceeds this limit and
+    :exc:`LookupError` is raised if ``lang_code`` exceeds this limit and
     ``strict`` is ``True``, or if there is no generic variant and ``strict``
     is ``False``.
 
@@ -1120,10 +1120,10 @@ For a complete discussion on the usage of the following see the
 
     Raises :exc:`LookupError` if nothing is found.
 
-    .. versionchanged:: 4.2.14
+    .. versionchanged:: 4.2.15
 
         In older versions, ``lang_code`` values over 500 characters were
-        processed without raising a :exc:`ValueError`.
+        processed without raising a :exc:`LookupError`.
 
 .. function:: to_locale(language)
 

docs/releases/4.2.15.txt

@@ -0,0 +1,14 @@
+===========================
+Django 4.2.15 release notes
+===========================
+
+*Expected August 6, 2024*
+
+Django 4.2.15 fixes a regression in 4.2.14.
+
+Bugfixes
+========
+
+* Fixed a regression in Django 4.2.14 that caused a crash in
+  ``LocaleMiddleware`` when processing a language code over 500 characters
+  (:ticket:`35627`).

docs/releases/5.0.8.txt

@@ -19,3 +19,7 @@ Bugfixes
 * Fixed a crash when creating a model with a ``Field.db_default`` and a
   ``Meta.constraints`` constraint composed of ``__endswith``, ``__startswith``,
   or ``__contains`` lookups (:ticket:`35625`).
+
+* Fixed a regression in Django 5.0.7 that caused a crash in
+  ``LocaleMiddleware`` when processing a language code over 500 characters
+  (:ticket:`35627`).

docs/releases/index.txt

@@ -48,6 +48,7 @@ versions of the documentation contain the release notes for any later releases.
 .. toctree::
    :maxdepth: 1
 
+   4.2.15
    4.2.14
    4.2.13
    4.2.12