#3667: Update the s3 post functionality to better support success_action_redirect (#3668)

* Update the s3 post functionality to better support success_action_redirect

- Add the bucket/key values to the redirect url like s3 does, which
supports code that relies on the key value being there on the
redirect.
- Add support for replacing ${filename} in the key value with the actual
filename from the form upload.

See Issue #3667

* Update s3 tests for changed success_action_redirect behavior

- Adds a new test called test_s3_server_post_to_bucket_redirect that
tests both the ${filename} replacement and the key/value addition to the
redirect query args
- Updated the test_creating_presigned_post checks to handle the
key/value additions to the redirect url.

* Fix test updates to work with python2.7

- remove f-string usage
- fix urllib.parse imports to use six

Co-authored-by: Wynn Wilkes <wynn@leading2lean.com>

tests/test_s3/test_s3.py

@@ -7,6 +7,7 @@ import os
 from boto3 import Session
 from six.moves.urllib.request import urlopen
 from six.moves.urllib.error import HTTPError
+from six.moves.urllib.parse import urlparse, parse_qs
 from functools import wraps
 from gzip import GzipFile
 from io import BytesIO
@@ -4814,9 +4815,11 @@ def test_creating_presigned_post():
         {"success_action_redirect": success_url},
     ]
     conditions.append(["content-length-range", 1, 30])
+
+    real_key = "{file_uid}.txt".format(file_uid=file_uid)
     data = s3.generate_presigned_post(
         Bucket=bucket,
-        Key="{file_uid}.txt".format(file_uid=file_uid),
+        Key=real_key,
         Fields={
             "content-type": "text/plain",
             "success_action_redirect": success_url,
@@ -4828,14 +4831,15 @@ def test_creating_presigned_post():
     resp = requests.post(
         data["url"], data=data["fields"], files={"file": fdata}, allow_redirects=False
     )
-    assert resp.headers["Location"] == success_url
     assert resp.status_code == 303
-    assert (
-        s3.get_object(Bucket=bucket, Key="{file_uid}.txt".format(file_uid=file_uid))[
-            "Body"
-        ].read()
-        == fdata
-    )
+    redirect = resp.headers["Location"]
+    assert redirect.startswith(success_url)
+    parts = urlparse(redirect)
+    args = parse_qs(parts.query)
+    assert args["key"][0] == real_key
+    assert args["bucket"][0] == bucket
+
+    assert s3.get_object(Bucket=bucket, Key=real_key)["Body"].read() == fdata
 
 
 @mock_s3