Python - 请求上传文件错误500

Question

我编写了以下代码，该代码应该使用请求将图像上传到名为Roblox的网站。

import requests
s = requests.session()
login_data = dict(username='USERNAMEHERE', password='PASSWORDHERE')
s.post('https://www.roblox.com/newlogin', data=login_data)
upload_data = dict(name="PythonUpload")
r = s.post('http://www.roblox.com/build/upload', files={'file': open('PythonDecalUploadTest.jpg', 'rb')}, data=upload_data)
print(r) #This returns a 500 error

这是发布到的表单。

<form action="/build/upload" enctype="multipart/form-data" id="upload-form" method="post">
            <input name="__RequestVerificationToken" type="hidden" value="H_69BCzd4bdyJ7EXalAOvaa-zeZZOvtQR-E9YHnCpmH9HVZKxHGrSVjAciLInCibyD8k432ZRzqX8d0MPPfCv-vOfAM1">
            <input id="assetTypeId" name="assetTypeId" type="hidden" value="13">
            <input id="isOggUploadEnabled" name="isOggUploadEnabled" type="hidden" value="True">
            <input id="groupId" name="groupId" type="hidden" value="">
            <input id="onVerificationPage" name="onVerificationPage" type="hidden" value="False">

            <div id="container">
                    <div class="form-row">
                        <label for="file">Find your image:</label>
                        <input id="file" type="file" name="file" tabindex="1">
                        <span id="file-error" class="error"></span>
                    </div>
                                    <div class="form-row">
                        <label for="name">Decal Name:</label>
                        <input id="name" type="text" class="text-box text-box-medium" name="name" maxlength="50" tabindex="2">
                        <span id="name-error" class="error"></span>
                    </div>
                                <div class="form-row submit-buttons">
                        <a id="upload-button" class="btn-medium btn-primary btn-level-element " tabindex="3">Upload</a>
                                                        <span id="loading-container">
                        <img src="http://images.rbxcdn.com/ec4e85b0c4396cf753a06fade0a8d8af.gif">
                    </span>
                </div>
            </div>
            </form>

我不确定请求验证令牌是什么，因此我只是更改了几个字母/数字以防万一。

那为什么这会返回500错误？为什么不上传我的图片？