fabric.js图像编辑库调试出错与django开发服务器

定义1个canvas

<div>
        <input type="color" value="#005E7A" id="drawing-color"><br>
        <canvas id="c" width="500" height="500" style="border:1px solid #aaa"></canvas>
    </div>

<script src="/static/fabric/fabric.js"></script>
    <script src="/static/fabric/lib/event.js"></script>
    <script>
        $(document).ready(function () {
            let canvas = new fabric.Canvas('c', {
                isDrawingMode: true
            });
            fabric.Object.prototype.transparentCorners = false;
            canvas.freeDrawingBrush.color = '#005E7A';
            $('#drawing-color').change(function () {
                canvas.freeDrawingBrush.color = this.value;
                console.log(this.value);
            });
            let rect = new fabric.Rect({
                left: 100,
                top: 100,
                fill: 'red',
                width: 20,
                height: 20,
                angle: 45
            });
            canvas.add(rect);

        });

使用django的开发服务器，会报各种莫名其妙的错误，点击鼠标后，涂鸦线连续不断。

Uncaught TypeError: fabric.Rect is not a constructor
Uncaught TypeError: Cannot read property 'prototype' of undefined
    at klass.initialize (fabric.js:13587)
    at klass.initialize (fabric.js:2149)
    at new klass (fabric.js:2214)
    at klass.createPath (fabric.js:5978)
    at klass._finalizeAndAddPath (fabric.js:6039)
    at klass.onMouseUp (fabric.js:5848)
    at klass._onMouseUpInDrawingMode (fabric.js:8876)
    at klass.__onMouseUp (fabric.js:8677)
    at klass._onMouseUp (fabric.js:8594)

切换到uwsgi+nginx则正常。