(merge) Fix #10154 and #10090: locale normalizes the UTF-8 encoding to "UTF-8" instead of "UTF8"

On MacOSX and OpenBSD (and possibly other BSDs) "en_US.UTF-8" is a valid locale
while "en_US.UTF8" is not. As the former works on Linux as well it is better
to normalize to that value.
diff --git a/Misc/NEWS b/Misc/NEWS
index e31d8b8..7db72e7 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -698,6 +698,9 @@
   and a non-zero offset, and an attempt to read past the end of file is made
   (IndexError is raised instead).  Patch by Ross Lagerwall.
 
+- Issue #10154, #10090: change the normalization of UTF-8 to "UTF-8" instead
+  of "UTF8" in the locale module as the latter is not supported MacOSX and OpenBSD.
+
 - Issue #10684: shutil.move used to delete a folder on case insensitive
   filesystems when the source and destination name where the same except
   for the case.