Submit HTTP Authentication credentials with Selenium. Note that although the methods exist, Selenium doesn't seem to support native HTTP Auth handling in Firefox.

selenium_http_auth.py

"""
Steven Englehardt
github.com/englehardt

Some dependencies (probably not exhaustive):
    sudo apt-get install python-Xlib scrot xserver-xephyr
    sudo pip install pyautogui pyvirtualdisplay

This needs access to a Firefox binary, and hardcodes a relative location.

NOTE: I've noticed that this won't work if you move the mouse during
      the demo. This only happens when the virtual display is visible,
      which won't be the case during most crawling.
"""
from selenium.webdriver.firefox.firefox_binary import FirefoxBinary
from selenium import webdriver

import pyvirtualdisplay
import threading
import pyautogui
import Xlib
import time

USER = 'httpwatch'
PASS = 'blah'
TEST_URL = 'https://www.httpwatch.com/httpgallery/authentication/authenticatedimage/default.aspx'
SCREEN_RES = (1366, 768)

# Start the virtualdisplay
display = pyvirtualdisplay.Display(visible=1, size=SCREEN_RES)
display.start()

# Attach pyautogui to virtual display
pyautogui._pyautogui_x11._display = Xlib.display.Display(display.new_display_var)

fb = FirefoxBinary('firefox/firefox')
driver = webdriver.Firefox(firefox_binary = fb)
driver.set_window_size(*SCREEN_RES)
driver.set_window_position(0,0)

def get_site_with_auth(driver):
    driver.get(TEST_URL)
    if driver.current_url == TEST_URL:
        print "Authentication Success!"
    else:
        print "Authentication Failed!"

# get site in a separate thread (since Selenium will block)
print "Getting site"
thread = threading.Thread(target=get_site_with_auth, args=(driver,))
thread.start()

# Use pyautogui to enter credentials
time.sleep(6)
print "Sending Auth Credentials"
pyautogui.typewrite(USER)
pyautogui.press('tab')
pyautogui.typewrite(PASS)
pyautogui.press('tab')
pyautogui.press('tab')
pyautogui.press('enter')

time.sleep(3)
driver.close()
display.stop()

Thanks. My environment is running Chrome headless with pyvirtualdisplay visibility set to 0. Your environment is Firefox with the pyvirtualdisplay visibility set to 1. Do I need to mimick yours?