from flask import Flask, render_template, request, jsonify
app = Flask(__name__)

from pymongo import MongoClient
import certifi

ca = certifi.where()

client = MongoClient('mongodb+srv://test:sparta@cluster0.a1ubwgr.mongodb.net/Cluster0?retryWrites=true&w=majority',tlsCAFile=ca)
db = client.dbsparta

@app.route('/')
def home():
   return render_template('index.html')

@app.route("/mars", methods=["POST"])
def web_mars_post():
    name_receive = request.form['name_give']
    address_receive = request.form['address_give']
    size_receive = request.form['size_give']

    doc = {
        'name':name_receive,
        'address':address_receive,
        'size':size_receive
    }
    db.mars.insert_one(doc)

    return jsonify({'msg': '주문 완료!'})

@app.route("/mars", methods=["GET"])
def web_mars_get():
    return jsonify({'msg': 'GET 연결 완료!'})

if __name__ == '__main__':
   app.run('0.0.0.0', port=5002, debug=True)

다른 분들과 달리 momgo db 진행시에 추가로 코드를 더 삽입해서 연결을 했었는데요.
이번 강의때 이게 오류가 된건지 안됩니다. (오류메시지 하단첨부)

/Users/leehyun/Desktop/sparta/projects/mars/venv/bin/python /Users/leehyun/Desktop/sparta/projects/mars/app.py 
Traceback (most recent call last):
  File "/Users/leehyun/Desktop/sparta/projects/mars/app.py", line 5, in <module>
    import certifi
ModuleNotFoundError: No module named 'certifi'