Python Selenium - How to pass UnexpectedAlertPresentException

Im trying to automate a web-game with python using selenium webdriver. There you have some missions and you have to send specific vehicles to a mission. You've a button where you can click on to choose a vehicle. If a vehicle is'nt available, a alert will present.

And that's the problem. I get an UnexpectedAlertPresentException and I tried to pass it like this:

try:   acc_veh_btn = driver.find_element_by_xpath("//*[@class='tab-    content']/div[{}]/div[1]/div[*]/a[@title='{}']".format(tab_index, acc_veh_name.strip())).click()   sleep(0.1)except UnexpectedAlertPresentException:   alert = driver.switch_to_alert()   alert.accept()   veh_ava = False   passelse:   pass

I don't know if this is the right way to handle this... anyway I get an UnexpectedAlertPresentException