Aggregate needed object instances for checker threads.
Create a new request session.
Aggregate(config, urlqueue, robots_txt, …)
Store thread-safe data collections for checker threads.
Store given link checking objects.
Print still-active URLs and empty the URL queue.
Add to number of downloaded bytes.
Add a request session for current thread.
Empty the URL queue.
Print ending output to log.
Wait for checker threads to finish.
Return iterator of checker threads.
Get the request session for current thread.
Determine if checking is finished.
Log all currently active threads.
Remove the stopped threads from the internal thread list.
Spawn threads for URL checking and status printing.
Check for a login URL and visit it.
Throttle requests to one host.