Fixed #29713 -- Added check that LANGUAGE_CODE uses standard language id format.

tests/check_framework/test_translation.py

@@ -0,0 +1,39 @@
+from django.core.checks.translation import check_setting_language_code
+from django.test import SimpleTestCase, override_settings
+
+
+class TranslationCheckTests(SimpleTestCase):
+
+    @override_settings(LANGUAGE_CODE="eu")
+    def test_valid_language_code_format_ll_only(self):
+        result = check_setting_language_code(None)
+        self.assertEqual(len(result), 0)
+
+    @override_settings(LANGUAGE_CODE="eü")
+    def test_invalid_language_code_format_ll_only(self):
+        result = check_setting_language_code(None)
+        self.assertEqual(len(result), 1)
+        error = result[0]
+        self.assertEqual(error.id, 'translation.E001')
+        self.assertEqual(error.msg, (
+            "LANGUAGE_CODE in settings.py is eü. It should be in the form ll or ll-cc where ll is the language and cc "
+            "is the country. Examples include: it, de-at, es, pt-br. The full set of language codes specifications is "
+            "outlined by https://en.wikipedia.org/wiki/IETF_language_tag#Syntax_of_language_tags"
+        ))
+
+    @override_settings(LANGUAGE_CODE="en-US")
+    def test_valid_language_code_format_ll_cc(self):
+        result = check_setting_language_code(None)
+        self.assertEqual(len(result), 0)
+
+    @override_settings(LANGUAGE_CODE="en_US")
+    def test_invalid_language_code_format_ll_cc(self):
+        result = check_setting_language_code(None)
+        self.assertEqual(len(result), 1)
+        error = result[0]
+        self.assertEqual(error.id, 'translation.E001')
+        self.assertEqual(error.msg, (
+            "LANGUAGE_CODE in settings.py is en_US. It should be in the form ll or ll-cc where ll is the language and "
+            "cc is the country. Examples include: it, de-at, es, pt-br. The full set of language codes specifications "
+            "is outlined by https://en.wikipedia.org/wiki/IETF_language_tag#Syntax_of_language_tags"
+        ))