urllib: urlretrieve() seems to ignore provided host header

從 urllib.request.urlretrieve()、build_opener() 和 opener.addheaders 著手，使用提供的 Windows/Python 3.10 範例重現 Host header 的行為。將請求 header 與 requests 範例進行比較，並判斷 Host 是否被刻意特殊處理；完成的標準是解釋清楚該行為，且如果確認這是 bug，則由 regression test 覆蓋。

Bug report

I have been having issues confirming this, but urlretrieve seems to ignore the provided Host header even if it's added. It seems to correctly look at User-agent and Referer. I have two functions doing the same download, one with urlretrieve and one with requests. The requests one works as expected and fails in the same way urlretrieve fails if I remove the Host header.

def download_helper(url, fname):
            opener = urllib.request.build_opener()
            opener.addheaders = [('User-agent', 'Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:103.0) Gecko/20100101 Firefox/103.0'),
                                ('Referer', "https://www.amd.com/en/support/graphics/amd-radeon-6000-series/amd-radeon-6700-series/amd-radeon-rx-6700-xt"),
                                ('Host' , 'us.download.nvidia.com')]
            urllib.request.install_opener(opener)
            import ssl
            ssl._create_default_https_context = ssl._create_unverified_context
            urllib.request.urlretrieve(url, filename=fname)

def download_helper2(url, fname):
    my_referer = "https://www.amd.com/en/support/graphics/amd-radeon-6000-series/amd-radeon-6700-series/amd-radeon-rx-6700-xt"
    resp = requests.get(url, verify=False, stream=True, headers={
        'referer': my_referer,
        'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:93.0) Gecko/20100101 Firefox/93.0',
        'Host' : 'us.download.nvidia.com'
        })
    total = int(resp.headers.get('content-length', 0))
    with open(fname, 'wb') as file:
        for data in resp.iter_content(chunk_size=1024):
            size = file.write(data)

download_helper2('https://192.229.211.70/Windows/516.94/516.94-desktop-win10-win11-64bit-international-dch-whql.exe', r'516.94-desktop-win10-win11-64bit-international-dch-whql.exe')

Your environment

• CPython versions tested on: 3.10.6
• Operating system and architecture: Windows Server 2022 10.0.20348.887 ; AMD64