Ticket #29886: django_patch3

diff --git a/django/db/backends/postgresql/base.py b/django/db/backends/postgresql/base.py
index ad6c504261..9de9b44735 100644
--- a/django/db/backends/postgresql/base.py
+++ b/django/db/backends/postgresql/base.py
@@ -121,7 +121,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
     #
     # Note: we use str.format() here for readability as '%' is used as a wildcard for
     # the LIKE operator.
-    pattern_esc = r"REPLACE(REPLACE(REPLACE({}, '\', '\\'), '%%', '\%%'), '_', '\_')"
+    pattern_esc = r"REPLACE(REPLACE(REPLACE({}, E'\\', E'\\\\'), E'%%', E'\\%%'), E'_', E'\\_')"
     pattern_ops = {
         'contains': "LIKE '%%' || {} || '%%'",
         'icontains': "LIKE '%%' || UPPER({}) || '%%'",
diff --git a/tests/postgres_tests/test_unaccent.py b/tests/postgres_tests/test_unaccent.py
index 018aedb64c..ccc1c53878 100644
--- a/tests/postgres_tests/test_unaccent.py
+++ b/tests/postgres_tests/test_unaccent.py
@@ -1,3 +1,4 @@
+from django.db import connection, DatabaseError
 from django.test import modify_settings
 
 from . import PostgreSQLTestCase
@@ -42,6 +43,24 @@ class UnaccentTest(PostgreSQLTestCase):
             ordered=False
         )
 
+    def test_unaccent_chained_with_conforming_strings_off(self):
+        """
+        Chained unaccent causes the comparison string to be escaped.
+        Make sure the escaping SQL is valid even if the DB has standard_conforming_strings OFF.
+        """
+        with connection.cursor() as cur:
+            cur.execute("SET standard_conforming_strings TO OFF;")
+            try:
+                self.assertQuerysetEqual(
+                    self.Model.objects.filter(field__unaccent__endswith="éÖ"),
+                    ["àéÖ", "aeO"],
+                    transform=lambda instance: instance.field,
+                    ordered=False
+                )
+            except DatabaseError:
+                self.fail("DatabaseError should not have occurred.")
+            cur.execute("SET standard_conforming_strings TO ON;")
+
     def test_unaccent_accentuated_needle(self):
         self.assertQuerysetEqual(
             self.Model.objects.filter(field__unaccent="aéÖ"),