PhantomJSCloud Error: Invalid Character ‘u’ – Python

I use PhantomJSCloud to take screenshots of web apps. While writing new code, I noticed this error coming back from the server:

{  
   "name":"HttpStatusCodeException",
   "statusCode":400,
   "message":"Error extracting userRequest. innerException: JSON5: invalid character 'u' at 1:1",
   "stack":[  
      "no stack unless env is DEV or TEST, or logLevel is DEBUG or TRACE"
   ]
}

The problem came because the request wasn’t JSON-encoding the object; the fix looks like this (using the requests library):

    post_data_string = json.dumps(python_object_here, sort_keys=True, indent=3, separators=(',', ': '))
    r = requests.post('https://phantomjscloud.com/api/browser/v2/', data=post_data_string)