Tkinter Messagebox doesn´t appear when called in perforce trigger script

Question

I am writing a script in Python 3.8.7 using the P4Python interface for our Perforce server. There are some circumstances where I don´t want to abort the submit of changes, but I need to inform the user about some information. For that purpose I wanted to use messagebox from the tkinter library. If the script get´s executed by perforce, the messagebox does not appear, but if I run it in a terminal, it works as expected.

Any clue how I can solve this problem.

Here is a code snippet of my script, where I want that the messagebox appears.

def setupConnection(cfg):
connectionError = False
exit = False
errorMsg = ""
while not exit:
    try:
        client = http.client.HTTPConnection(cfg.serverAddress)
        client.connect()        
    except: 
        connectionError = True        
        errorMsg = "Address " + cfg.serverAddress + " is not available! Check connection or configuration."
        #sys.exit("Address " + cfg.serverAddress + " is not available! Check connection or configuration.")

    if not connectionError:
        client.request(method=GET, url=cfg.apiAddress, headers=cfg.headers)
        response = client.getresponse()
        if response.status == pageNotFound404:
            connectionError = True
            errorMsg = "Address " + cfg.apiAddress + " is not available! Check connection or configuration."
            #sys.exit("Address " + cfg.apiAddress + " is not available! Check connection or configuration.")
        else:
            cfg.apiGetResponse = (response.read()).decode()
            exit = True
            return client
    if connectionError:  
        window = Tk()
        window.eval('tk::PlaceWindow %s center' % window.winfo_toplevel())
        window.withdraw()
        if not messagebox.askretrycancel('Connection error', errorMsg, icon='error'):
            exit = True              
            errorMsg = ('Please add changelist ' + cfg.changelist_ID + ' in ' + cfg.customFieldName + ' textbox of workpackage ' + cfg.workpackage_ID)
            messagebox.showinfo('User action required', errorMsg)
        window.destroy()
        window.quit()
        return None

Answer 1

Triggers are defined and executed on the server. If you pop a message box up on the server, the client isn't going to see it. Instead, your script should print the message to stdout; the server will pick it up and send it to the client (which can print it to the console or put it in a GUI window or whatever is appropriate to that client app).

https://www.perforce.com/perforce/doc.current/manuals/p4sag/Content/P4SAG/scripting.triggers.basics.html#Communic