Crawler project: fix error caused by aiohttp update that use URL object replace url str

[gasxia]

Clawler project use aiohttp version 0.21.But now aiohttp version is 2.0.7
Since aiohttp 1.1 the library uses yarl for URL processing, instead of url string.
That result in some str parsing errors.

So must change code to adapt the aiohttp new version.

use URL.human_repr() to print a humanable string.
change response.url type to fix error.
Line 146 File crawling.py:

                if urls:
                    LOGGER.info('got %r distinct urls from %r',
                                len(urls), response.url.human_repr())
                for url in urls:
                    normalized = urllib.parse.urljoin(str(response.url), url)
                    defragmented, frag = urllib.parse.urldefrag(normalized)
                    if self.url_allowed(defragmented):
                        links.add(defragmented)

change _stat.url type to fix error.
Line 32 File reporting.py

show.sort(key=lambda _stat: str(_stat.url))