Fixed #27138 -- Restored pre-Python 3.6 behavior of localtime() and make_naive() on Python 3.6.

Reverted test changes in a7a7ecd2 and
e43ea36b (refs #27025).

AUTHORS

@@ -364,6 +364,7 @@ answer newbie questions, and generally made Django that much better:
     Jim Dalton <jim.dalton@gmail.com>
     Jimmy Song <jaejoon@gmail.com>
     Jiri Barton
+    Joachim Jablon <ewjoachim@gmail.com>
     Joao Oliveira <joaoxsouls@gmail.com>
     Joe Heck <http://www.rhonabwy.com/wp/>
     Joel Bohman <mail@jbohman.com>

django/utils/timezone.py

@@ -209,8 +209,9 @@ def localtime(value=None, timezone=None):
         value = now()
     if timezone is None:
         timezone = get_current_timezone()
-    # If `value` is naive, astimezone() will raise a ValueError,
-    # so we don't need to perform a redundant check.
+    # Emulate the behavior of astimezone() on Python < 3.6.
+    if is_naive(value):
+        raise ValueError("localtime() cannot be applied to a naive datetime")
     value = value.astimezone(timezone)
     if hasattr(timezone, 'normalize'):
         # This method is available for pytz time zones.
@@ -295,8 +296,9 @@ def make_naive(value, timezone=None):
     """
     if timezone is None:
         timezone = get_current_timezone()
-    # If `value` is naive, astimezone() will raise a ValueError,
-    # so we don't need to perform a redundant check.
+    # Emulate the behavior of astimezone() on Python < 3.6.
+    if is_naive(value):
+        raise ValueError("make_naive() cannot be applied to a naive datetime")
     value = value.astimezone(timezone)
     if hasattr(timezone, 'normalize'):
         # This method is available for pytz time zones.

tests/utils_tests/test_timezone.py

 import datetime
 import pickle
-import sys
 
 import pytz
 
@@ -11,8 +10,6 @@ CET = pytz.timezone("Europe/Paris")
 EAT = timezone.get_fixed_timezone(180)      # Africa/Nairobi
 ICT = timezone.get_fixed_timezone(420)      # Asia/Bangkok
 
-PY36 = sys.version_info >= (3, 6)
-
 
 class TimezoneTests(SimpleTestCase):
 
@@ -24,14 +21,10 @@ class TimezoneTests(SimpleTestCase):
 
     def test_localdate(self):
         naive = datetime.datetime(2015, 1, 1, 0, 0, 1)
-        if PY36:
-            self.assertEqual(timezone.localdate(naive), datetime.date(2015, 1, 1))
-            self.assertEqual(timezone.localdate(naive, timezone=EAT), datetime.date(2015, 1, 1))
-        else:
-            with self.assertRaisesMessage(ValueError, 'astimezone() cannot be applied to a naive datetime'):
-                timezone.localdate(naive)
-            with self.assertRaisesMessage(ValueError, 'astimezone() cannot be applied to a naive datetime'):
-                timezone.localdate(naive, timezone=EAT)
+        with self.assertRaisesMessage(ValueError, 'localtime() cannot be applied to a naive datetime'):
+            timezone.localdate(naive)
+        with self.assertRaisesMessage(ValueError, 'localtime() cannot be applied to a naive datetime'):
+            timezone.localdate(naive, timezone=EAT)
 
         aware = datetime.datetime(2015, 1, 1, 0, 0, 1, tzinfo=ICT)
         self.assertEqual(timezone.localdate(aware, timezone=EAT), datetime.date(2014, 12, 31))
@@ -133,12 +126,8 @@ class TimezoneTests(SimpleTestCase):
             timezone.make_naive(datetime.datetime(2011, 9, 1, 17, 20, 30, tzinfo=ICT), EAT),
             datetime.datetime(2011, 9, 1, 13, 20, 30))
 
-        args = (datetime.datetime(2011, 9, 1, 13, 20, 30), EAT)
-        if PY36:
-            self.assertEqual(timezone.make_naive(*args), datetime.datetime(2011, 9, 1, 21, 20, 30))
-        else:
-            with self.assertRaisesMessage(ValueError, 'astimezone() cannot be applied to a naive datetime'):
-                timezone.make_naive(*args)
+        with self.assertRaisesMessage(ValueError, 'make_naive() cannot be applied to a naive datetime'):
+            timezone.make_naive(datetime.datetime(2011, 9, 1, 13, 20, 30), EAT)
 
     def test_make_naive_no_tz(self):
         self.assertEqual(
@@ -168,14 +157,8 @@ class TimezoneTests(SimpleTestCase):
                 pytz.timezone("Asia/Bangkok").localize(datetime.datetime(2011, 9, 1, 17, 20, 30)), CET
             ),
             datetime.datetime(2011, 9, 1, 12, 20, 30))
-        if PY36:
-            self.assertEqual(
-                timezone.make_naive(datetime.datetime(2011, 9, 1, 12, 20, 30), CET),
-                datetime.datetime(2011, 9, 1, 19, 20, 30)
-            )
-        else:
-            with self.assertRaises(ValueError):
-                timezone.make_naive(datetime.datetime(2011, 9, 1, 12, 20, 30), CET)
+        with self.assertRaisesMessage(ValueError, 'make_naive() cannot be applied to a naive datetime'):
+            timezone.make_naive(datetime.datetime(2011, 9, 1, 12, 20, 30), CET)
 
     def test_make_aware_pytz_ambiguous(self):
         # 2:30 happens twice, once before DST ends and once after