[2.0.x] Fixed #28710 -- Fixed the Basque DATE_FORMAT string

Thanks Eneko Illarramendi for the report and initial patch.
Backport of 8c538871bd from master.

django/conf/locale/eu/formats.py

@@ -2,7 +2,7 @@
 #
 # The *_FORMAT strings use the Django date format syntax,
 # see http://docs.djangoproject.com/en/dev/ref/templates/builtins/#date
-DATE_FORMAT = r'Yeko M\re\n d\a'
+DATE_FORMAT = r'Y\k\o N j\a'
 TIME_FORMAT = 'H:i'
 # DATETIME_FORMAT =
 # YEAR_MONTH_FORMAT =

docs/releases/1.11.7.txt

@@ -11,3 +11,5 @@ Bugfixes
 
 * Prevented ``cache.get_or_set()`` from caching ``None`` if the ``default``
   argument is a callable that returns ``None`` (:ticket:`28601`).
+
+* Fixed the Basque ``DATE_FORMAT`` string (:ticket:`28710`).

tests/i18n/tests.py

@@ -9,6 +9,7 @@ from threading import local
 
 from django import forms
 from django.conf import settings
+from django.conf.locale import LANG_INFO
 from django.conf.urls.i18n import i18n_patterns
 from django.template import Context, Template
 from django.test import (
@@ -335,6 +336,23 @@ class FormattingTests(SimpleTestCase):
             'l': self.long,
         })
 
+    def test_all_format_strings(self):
+        all_locales = LANG_INFO.keys()
+        today = datetime.date.today()
+        now = datetime.datetime.now()
+        current_year = str(today.year)
+        current_day = str(today.day)
+        current_minute = str(now.minute)
+        for locale in all_locales:
+            with self.subTest(locale=locale), translation.override(locale):
+                self.assertIn(current_year, date_format(today))  # Uses DATE_FORMAT by default
+                self.assertIn(current_minute, time_format(now))  # Uses TIME_FORMAT by default
+                self.assertIn(current_year, date_format(now, format=get_format('DATETIME_FORMAT')))
+                self.assertIn(current_year, date_format(today, format=get_format('YEAR_MONTH_FORMAT')))
+                self.assertIn(current_day, date_format(today, format=get_format('MONTH_DAY_FORMAT')))
+                self.assertIn(current_year, date_format(today, format=get_format('SHORT_DATE_FORMAT')))
+                self.assertIn(current_year, date_format(now, format=get_format('SHORT_DATETIME_FORMAT')))
+
     def test_locale_independent(self):
         """
         Localization of numbers