[3.7] bpo-20087: Update locale alias mapping with glibc 2.27 supported locales. (GH-6708) (GH-6713)

(cherry picked from commit cedc9b74202d8c1ae39bca261cbb45d42ed54d45)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
diff --git a/Lib/test/test_locale.py b/Lib/test/test_locale.py
index d93b3ad..e2c2178 100644
--- a/Lib/test/test_locale.py
+++ b/Lib/test/test_locale.py
@@ -441,7 +441,7 @@
 
     def test_valencia_modifier(self):
         self.check('ca_ES.UTF-8@valencia', 'ca_ES.UTF-8@valencia')
-        self.check('ca_ES@valencia', 'ca_ES.ISO8859-15@valencia')
+        self.check('ca_ES@valencia', 'ca_ES.UTF-8@valencia')
         self.check('ca@valencia', 'ca_ES.ISO8859-1@valencia')
 
     def test_devanagari_modifier(self):