Reading a refreshing jpg image on a webserver and viewing within Tkinter

Ok so for a project I have been trying to view a stream from a really old cctv camera (I have the owners permission) and the way it works is with a single set path ("/cgi-bin/viewer/video.jpg") which is a constantly changing jpg image. I am able to view it through VLC (with an incredibly unintuitive setup) or by constantly refreshing the aforementioned path. So what I am trying to do is make a program to read the image data and display it in tkinter, and then repeat it every couple seconds.

import io 
from PIL import Image,ImageTk
# makes it backwards compatible
try:
    import Tkinter as tk
    from urllib2 import urlopen
except ImportError:
    import tkinter as tk
    from urllib.request import urlopen

stage=tk.Tk()
stage.title("jpg stream test")

url="http://<url>:<port>/cgi-bin/viewer/video.jpg"

def test(url):
    img_url=urlopen(url)
    img_data=io.BytesIO(img_url.read())
    img_pil=Image.open(img_data).resize((1000,800))
    img_tk=ImageTk.PhotoImage(img_pil)
    panel.configure(image=img_tk)
    stage.after(200, test(url)) # I have tried upping the delay, it did nothing

panel=tk.Label(stage,image=ImageTk.PhotoImage(Image.open("placeholder.jpg"))) # tried it without placeholder
panel.pack(side="bottom",fill="both",expand=True)

stage.after(500,test(url))

stage.mainloop()

Now I am fairly new to programming as a whole let alone tkinter, when I run this code it opens up to a white empty window, and stays that way. Though I did note when taking all the code out of the test() function and removing all instances of stage.after() I could get a single image from the webstream with 0 issues. I am not sure what could possibly be causing it to not work. This is my 5th attempt.

Revised code (thanks to @acw1668):

import io 
from PIL import Image,ImageTk
# makes it backwards compatible
try:
    import Tkinter as tk
    from urllib2 import urlopen
except ImportError:
    import tkinter as tk
    from urllib.request import urlopen

stage=tk.Tk()
stage.title("jpg stream test")

url="http://<url>:<port>/cgi-bin/viewer/video.jpg"

def test(url):
    img_url=urlopen(url)
    img_data=io.BytesIO(img_url.read())
    img_pil=Image.open(img_data).resize((1000,800))
    img_tk=ImageTk.PhotoImage(img_pil)
    panel.configure(image=img_tk)
    panel.image= img_tk
    stage.after(200, test, url) 

panel=tk.Label(stage,image=ImageTk.PhotoImage(Image.open("placeholder.jpg"))) 
panel.pack(side="bottom",fill="both",expand=True)

stage.after(500, test, url)

stage.mainloop()