Mongodb Flask 错误请求浏览器发送了此服务器无法理解的请求

我正在try 上传文件&amp；使用flask将数据任务输入我的MongoDB

Bad Request

我的HTML代码

    <form class="form-check form-control" method="post" enctype="multipart/form-data" action="{{ url_for('index') }}">      
          <label>Full Name*</label></td>
          <input name="u_name" type="text" class="text-info my-input" required="required" />
          <label>Email*</label>
          <input name="u_email" type="email" class="text-info my-input" required="required" />
          <label>Password*</label>
          <input name="u_pass" type="password" class="text-info my-input" required="required" />
          <label>Your Image*</label>
          <input name="u_img" type="file" class="text-info" required="required" /></td>
          <input name="btn_submit" type="submit" class="btn-info" />
    </form>

&amp；我的python代码:

from flask import Flask, render_template, request, url_for
from flask_pymongo import PyMongo
import os
app = Flask(__name__)
app.config['MONGO_DBNAME'] = 'flask_assignment'
app.config['MONGO_URI'] = 'mongodb://<user>:<pass>@<host>:<port>/<database>'
mongo = PyMongo(app)
app_root = os.path.dirname(os.path.abspath(__file__))


@app.route('/', methods=['GET', 'POST'])
def index():
    target = os.path.join(app_root, 'static/img/')
    if not os.path.isdir(target):
        os.mkdir(target)
    if request.method == 'POST':
        name = request.form['u_name']
        password = request.form['u_pass']
        email = request.form['u_email']
        file_name = ''
        for file in request.form['u_img']:
            file_name = file.filename
            destination = '/'.join([target, file_name])
            file.save(destination)
        mongo.db.employee_entry.insert({'name': name, 'password': password, 'email': email, 'img_name': file_name})
        return render_template('index.html')
    else:
        return render_template('index.html')

app.run(debug=True)