I am using version 0.8.12 of mws and I have a little code that does a feed submit.

In my development environment which I have running on venv with python 3.9.2, I am getting an error from amazon that looks like this:

mws.mws.MWSError: <?xml version="1.0"?>
<ErrorResponse xmlns="http://mws.amazonaws.com/doc/2009-01-01/">
  <Error>
    <Type>Sender</Type>
    <Code>InvalidParameterValue</Code>
    <Message>Timestamp 2021-03-10T20%3A08%3A42 must be in ISO8601 format</Message>
  </Error>
  <RequestID>1d289d47-28e6-4352-a3e4-33657df32e96</RequestID>
</ErrorResponse>

Digging through the stack trace it looks like amazon seems to be choking on the timestamp that is generated by the relatively new function mws_utc_now() which lives in /mws/future_utils/timezone.py.

Does the error message look like it might be an encoding issue for the timestamp that is being sent to amazon? Or is amazon url-encoding what they are sending back in the error message?

FWIW, the same code that is causing the error above works fine on the production server under python 3.6.9 and mws version 0.8.6 (which is before mws_utc_now was released in version 0.8.11).