Fix S3Boto3: Double localtime call Exception on modified_time when US…

…E_TZ=False jschneier#234

AUTHORS

@@ -25,6 +25,7 @@ By order of apparition, thanks:
     * Anthony Monthe (Dropbox)
     * EunPyo (Andrew) Hong (Azure)
     * Michael Barrientos (S3 with Boto3)
+    * piglei (patches)
 
 Extra thanks to Marty for adding this in Django,
 you can buy his very interesting book (Pro Django).

storages/backends/s3boto3.py

@@ -11,7 +11,7 @@
 from django.utils.encoding import force_text, smart_str, filepath_to_uri, force_bytes
 from django.utils.six.moves.urllib import parse as urlparse
 from django.utils.six import BytesIO
-from django.utils.timezone import localtime
+from django.utils.timezone import localtime, is_naive
 
 try:
     from boto3 import resource
@@ -534,7 +534,12 @@ def get_modified_time(self, name):
 
     def modified_time(self, name):
         """Returns a naive datetime object containing the last modified time."""
-        return localtime(self.get_modified_time(name)).replace(tzinfo=None)
+        # If get_modified_time already returns a naive DateTime object, which happens 
+        # when USE_TZ=False, return it directly instead of transfer it.
+        mtime = self.get_modified_time(name)
+        if is_naive(mtime):
+            return mtime
+        return localtime(mtime).replace(tzinfo=None)
 
     def _strip_signing_parameters(self, url):
         # Boto3 does not currently support generating URLs that are unsigned. Instead we

tests/test_s3boto3.py

@@ -6,6 +6,7 @@
     import mock
 
 from django.test import TestCase
+from django.conf import settings
 from django.core.files.base import ContentFile
 from django.utils.six.moves.urllib import parse as urlparse
 from django.utils.timezone import is_aware, utc
@@ -274,6 +275,12 @@ def test_storage_size(self):
         self.assertEqual(self.storage.size(name), obj.content_length)
 
     def test_storage_mtime(self):
+        # Test both USE_TZ cases
+        for use_tz in (True, False):
+            with self.settings(USE_TZ=use_tz):
+                self._test_storage_mtime(use_tz)
+
+    def _test_storage_mtime(self, use_tz):
         obj = self.storage.bucket.Object.return_value
         obj.last_modified = datetime.now(utc)
 
@@ -283,9 +290,13 @@ def test_storage_mtime(self):
             'Naive datetime object expected from modified_time()'
         )
 
-        self.assertTrue(
+        self.assertIs(
+            settings.USE_TZ,
             is_aware(self.storage.get_modified_time(name)),
-            'Aware datetime object expected from get_modified_time()'
+            '%s datetime object expected from get_modified_time() when USE_TZ=%s' % (
+                ('Naive', 'Aware')[settings.USE_TZ],
+                settings.USE_TZ
+            )
         )
 
     def test_storage_url(self):