Selenium tests - Everything is printed all the time no matter what

This might sound like a very silly question but here it is:

I'm writing selenium tests in python, and basically my base test class looks like that:

chromedriver = "../selenium-tests/chromedriver"
os.environ["webdriver.chrome.driver"] = chromedriver

class TestsFoo(unittest.TestCase):
    base_url = None
    language = None

    def setUp(self):
        self.driver = webdriver.Chrome(chromedriver)
        self.verificationErrors = []
        self.accept_next_alert = True
        self.driver.set_window_size(1100, 800)

Then all of my other test classes extend from that class. Example:

class TestsFooChild(TestsFoo):
    def test_something(self):
        driver = self.driver
        driver.get("{}{}/myurl.html".format(
            self.base_url,
            self.language)
        )
        # do stuff

        print driver.current_url
        self.assertTrue(somethingTrue)

    def tearDown(self):
        self.driver.close()
        self.driver.quit()

language and url are defined thanks to this:

if __name__ == "__main__":
    TestsFoo.base_url = os.environ.get('URL')
    TestsFoo.language = os.environ.get('LANGUAGE')
    unittest.main()

So that's a lot of informations for a very very tiny question: When doing unittest, if you let a print somewhere, it'll only be printed if the test fails.

Then why in my case, are every prints printed no matter what the result of the test is? I only want to print my current_url when the test fails.

Also, I'm just looking at why it does that. I'm actively working on finding a way to only print it when my test fails. So that part is taken care of. But I'm curious..