AWS和Flask文件上传/下载

Question

我使用Zappa（后面使用AWS和S3）托管了我的Flask Web应用程序。我的申请涉及上传和下载文件。当我尝试执行上述任一操作时，出现以下错误。

IOError：[Errno 30]只读文件系统

为什么S3阻止上传/下载以及如何将其更改为可读写？

您可以访问托管应用here

@app.route('/paper_upload',methods=['POST','GET'])
def paper_upload(): # Journal Upload
    if  request.method == 'POST' and 'file' in request.files:
        filename = files.save(request.files['file'])

        doc = Journal(title=request.form['Title'],user_email=session['email'],
                    domain=request.form['domain'],status="Submission received",filename=filename,date=datetime.datetime.utcnow())
        doc.save()
        flash('Journal Submitted')
        return redirect(url_for('dashboard'))

@app.route('/download/<filename>',methods=['POST','GET'])
def download(filename):
    return send_file(safe_join('app.config['UPLOADED_FILES_DEST']',filename),as_attachment=True)