wsgiref validator complaining about no content-type when it is not needed

Bug report

https://github.com/python/cpython/blob/main/Lib/wsgiref/validate.py#L70 says that it wants to check

• That no Content-Type is given when there is no content

However, the code's behaviour appears not to match that.

The code notes there was uncertainty: https://github.com/python/cpython/blob/main/Lib/wsgiref/validate.py#L417
But more importantly, its behaviour is a contradiction with the stated objective mentioned above, as I interpret this.
I also cannot see where RFC2616 (which has been obsoleted by others, it would seem) mandates that behaviour.

In the following example, there is no content, and the validator complains about no Content-Type:

#!/usr/bin/env python3

from wsgiref.simple_server import make_server
from wsgiref.validate import validator

def wsgi_callable(environ, start_response):
	start_response('302 Found', [('Location', 'https://example.com/')])
	return [] # same result with None

make_server(host='localhost', port=8080, app=validator(wsgi_callable)).serve_forever()

When I make a request with curl localhost:8080, this error appears:

Traceback (most recent call last):
  File "/usr/lib/python3.10/wsgiref/handlers.py", line 137, in run
    self.result = application(self.environ, self.start_response)
  File "/usr/lib/python3.10/wsgiref/validate.py", line 181, in lint_app
    iterator = application(environ, start_response_wrapper)
  File "/home/calimero/test.py", line 7, in wsgi_callable
    start_response('302 Found', [('Location', 'https://example.com/')])
  File "/usr/lib/python3.10/wsgiref/validate.py", line 172, in start_response_wrapper
    check_content_type(status, headers)
  File "/usr/lib/python3.10/wsgiref/validate.py", line 428, in check_content_type
    assert_(0, "No Content-Type header found in headers (%s)" % headers)
  File "/usr/lib/python3.10/wsgiref/validate.py", line 128, in assert_
    raise AssertionError(*args)
AssertionError: No Content-Type header found in headers ([('Location', 'https://example.com/')])

Your environment

• CPython version tested on: 3.10.4
• Operating system and architecture: Archlinux x86-64

从 Lib/wsgiref/validate.py 开始，重点查看第 70 行附近的描述、第 417 行附近提到的不确定性，以及第 428 行附近的 check_content_type。使用验证器重现重定向示例，并检查相关的 WSGI 或 HTTP 要求。当验证器的行为与所述目标一致，并且针对所报告案例有回归测试覆盖时，即视为完成。