The python script is continuously running

[ibreeden]

The repetition is in the Scanner.crawl() method. This method is recursively calling itself in line 56. When the first page contains a link to itself, the crawl will start again from the begin. Obviously this does not need to be the first page, this behaviour would always occur.
I see the __init__() method initializes self.target_links = [] which is not used. I would suggest to make target_links a set instead of a list and use it to filter links already visited. (Because sets can easily be filtered, for example: return urls - self.target_links.)