Unable to capture the alert in Selenium using Python

I am trying to test a web portal using Selenium and Python. The problem is, I am unable to get around an error, in other words, I am unable to catch the alert.

Scenario:

Search for a user, if the user is not found, the website throws an error. I have a list that contains valid and invalid users to perform the search upon. When the search is successful, there are a few links I need to click to get to the user. If the user is not found, the links won’t be displayed and an error is displayed instead. The problem is when I search for an invalid user, the code is looking for the links that are displayed when the a valid user is displayed.

Code:

from selenium import webdriver
from selenium.webdriver.chrome.webdriver import WebDriver
from selenium.webdriver.support.select import Select
from selenium.webdriver.common.keys import Keys
from selenium.webdriver.support.ui import Select
from selenium.common.exceptions import TimeoutException
from selenium.webdriver.support import expected_conditions as EC
from selenium.webdriver.common.alert import Alert
from selenium.common.exceptions import NoAlertPresentException
import time

browser = webdriver.Chrome()  # type: WebDriver is Chrome
browser.get("https:URL")



if option == 'number':
            nums = ['111', '123', '456']
            searchbox = browser.find_element_by_id("searchPattern")
            noUser = browser.find_element_by_xpath('//*[@id="includeError"]/div')
            try:
                for num in nums:
                    searchbox.send_keys(num)
                    browser.find_element_by_xpath('//[@id="User"]/input[2]').click()
                    time.sleep(4)
                    user_links = ['photos', 'message', 'mails']
                    for url in user_links:
                        if url in user_links:
                            browser.find_element_by_link_text(url).click()
                            time.sleep(4)
                        elif url not in user_links:
                            print "No users found"
                    browser.switch_to_window(browser.window_handles[0])
                    time.sleep(5)
                    browser.find_element_by_id('searchPattern').clear()
            except noUser:
                print "no users"

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