urllib.request.urlopen(data_uri).file are closed automatically when the response is not hold by a variable

Bug report

Opening a data uri with urllib.request.urlopen and read it directly will result in I/O operation on closed file..

Errored example:

from urllib.request import urlopen

url = 'data:text/plain,hello world'
print(urlopen(url).file.read())

"""
Output:

Traceback (most recent call last):
  File "/home/maple3142/tmp/xa.py", line 4, in <module>
    print(urlopen(url).file.read())
ValueError: I/O operation on closed file.
"""

Normal example:

from urllib.request import urlopen

url = 'data:text/plain,hello world'
resp = urlopen(url)
print(resp.file.read())

"""
Output:

b'hello world'
"""

Your environment

• CPython versions tested on: 3.8.11, 3.10.4
• Operating system and architecture: Arch Linux on WSL2 on Windows 10 x64

先复现 urllib.request.urlopen 的两个示例，然后检查该入口点背后的 data-URI 处理。完成标准是直接链式调用 .file.read() 能够正常工作且不会出现文件已关闭错误，同时现有的存储响应示例仍然正确，并为该行为添加回归测试。