S3: Workaround boto bug to fix collectstatic issue

storages/backends/s3boto3.py

@@ -16,8 +16,8 @@
 
 from storages.base import BaseStorage
 from storages.utils import (
-    check_location, get_available_overwrite_name, lookup_env, safe_join,
-    setting,
+    NonCloseableBufferedReader, check_location, get_available_overwrite_name,
+    lookup_env, safe_join, setting,
 )
 
 try:
@@ -445,7 +445,8 @@ def _save(self, name, content):
 
         obj = self.bucket.Object(name)
         content.seek(0, os.SEEK_SET)
-        obj.upload_fileobj(content, ExtraArgs=params)
+        with NonCloseableBufferedReader(content) as reader:
+            obj.upload_fileobj(reader, ExtraArgs=params)
         return cleaned_name
 
     def delete(self, name):

storages/utils.py

@@ -1,3 +1,4 @@
+import io
 import os
 import posixpath
 
@@ -117,3 +118,10 @@ def get_available_overwrite_name(name, max_length):
             'allows sufficient "max_length".' % name
         )
     return os.path.join(dir_name, "{}{}".format(file_root, file_ext))
+
+
+# A buffered reader that does not actually close, workaround for
+# https://github.com/boto/s3transfer/issues/80#issuecomment-562356142
+class NonCloseableBufferedReader(io.BufferedReader):
+    def close(self):
+        self.flush()

tests/test_s3boto3.py

@@ -22,6 +22,12 @@ def setUp(self):
         self.storage._connections.connection = mock.MagicMock()
 
 
+def assert_called_upload(mock_uploadobj, content, extra):
+    assert mock_uploadobj.call_count == 1
+    assert mock_uploadobj.call_args[0][0].raw == content
+    assert mock_uploadobj.call_args[1] == extra
+
+
 class S3Boto3StorageTests(S3Boto3TestCase):
 
     def test_clean_name(self):
@@ -107,12 +113,12 @@ def test_storage_save(self):
         self.storage.bucket.Object.assert_called_once_with(name)
 
         obj = self.storage.bucket.Object.return_value
-        obj.upload_fileobj.assert_called_with(
-            content,
-            ExtraArgs={
+        extra = {
+            'ExtraArgs': {
                 'ContentType': 'text/plain',
             }
-        )
+        }
+        assert_called_upload(obj.upload_fileobj, content, extra)
 
     def test_storage_save_with_default_acl(self):
         """
@@ -125,13 +131,13 @@ def test_storage_save_with_default_acl(self):
         self.storage.bucket.Object.assert_called_once_with(name)
 
         obj = self.storage.bucket.Object.return_value
-        obj.upload_fileobj.assert_called_with(
-            content,
-            ExtraArgs={
+        extra = {
+            'ExtraArgs': {
                 'ContentType': 'text/plain',
                 'ACL': 'private',
             }
-        )
+        }
+        assert_called_upload(obj.upload_fileobj, content, extra)
 
     def test_storage_object_parameters_not_overwritten_by_default(self):
         """
@@ -145,13 +151,13 @@ def test_storage_object_parameters_not_overwritten_by_default(self):
         self.storage.bucket.Object.assert_called_once_with(name)
 
         obj = self.storage.bucket.Object.return_value
-        obj.upload_fileobj.assert_called_with(
-            content,
-            ExtraArgs={
+        extra = {
+            'ExtraArgs': {
                 'ContentType': 'text/plain',
                 'ACL': 'private',
             }
-        )
+        }
+        assert_called_upload(obj.upload_fileobj, content, extra)
 
     def test_content_type(self):
         """
@@ -164,12 +170,12 @@ def test_content_type(self):
         self.storage.bucket.Object.assert_called_once_with(name)
 
         obj = self.storage.bucket.Object.return_value
-        obj.upload_fileobj.assert_called_with(
-            content,
-            ExtraArgs={
+        extra = {
+            'ExtraArgs': {
                 'ContentType': 'image/jpeg',
             }
-        )
+        }
+        assert_called_upload(obj.upload_fileobj, content, extra)
 
     def test_storage_save_gzipped(self):
         """
@@ -179,13 +185,13 @@ def test_storage_save_gzipped(self):
         content = ContentFile("I am gzip'd")
         self.storage.save(name, content)
         obj = self.storage.bucket.Object.return_value
-        obj.upload_fileobj.assert_called_with(
-            content,
-            ExtraArgs={
+        extra = {
+            'ExtraArgs': {
                 'ContentType': 'application/octet-stream',
                 'ContentEncoding': 'gzip',
             }
-        )
+        }
+        assert_called_upload(obj.upload_fileobj, content, extra)
 
     def test_storage_save_gzip(self):
         """