#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_server.py

@@ -1,6 +1,8 @@
 # coding=utf-8
 
 from __future__ import unicode_literals
+import io
+from six.moves.urllib.parse import urlparse, parse_qs
 import sure  # noqa
 
 from flask.testing import FlaskClient
@@ -80,6 +82,39 @@ def test_s3_server_post_to_bucket():
     res.data.should.equal(b"nothing")
 
 
+def test_s3_server_post_to_bucket_redirect():
+    test_client = authenticated_client()
+
+    res = test_client.put("/", "http://tester.localhost:5000/")
+    res.status_code.should.equal(200)
+
+    redirect_base = "https://redirect.com/success/"
+    filecontent = "nothing"
+    filename = "test_filename.txt"
+    res = test_client.post(
+        "/",
+        "https://tester.localhost:5000/",
+        data={
+            "key": "asdf/the-key/${filename}",
+            "file": (io.BytesIO(filecontent.encode("utf8")), filename),
+            "success_action_redirect": redirect_base,
+        },
+    )
+    real_key = "asdf/the-key/{}".format(filename)
+    res.status_code.should.equal(303)
+    redirect = res.headers["location"]
+    assert redirect.startswith(redirect_base)
+
+    parts = urlparse(redirect)
+    args = parse_qs(parts.query)
+    assert args["key"][0] == real_key
+    assert args["bucket"][0] == "tester"
+
+    res = test_client.get("/{}".format(real_key), "http://tester.localhost:5000/")
+    res.status_code.should.equal(200)
+    res.data.should.equal(filecontent.encode("utf8"))
+
+
 def test_s3_server_post_without_content_length():
     test_client = authenticated_client()