Infinite loop when verify is invalid UNC path

[tl-hbk]

When an invalid UNC path is passed to requests.utils.extract_zipped_paths it results in an infinite loop

Expected Result

For extract_zipped_paths to return the path and an Exception to be thrown when the cert path is checked prior to verification being attempted.

Actual Result

Code gets stuck looping here

requests/requests/utils.py

Lines 245 to 248 in 5855dd7

	archive, member = os.path.split(path)
	while archive and not os.path.exists(archive):
	archive, prefix = os.path.split(archive)
	member = '/'.join([prefix, member])

Reproduction Steps

import requests.utils
requests.utils.extract_zipped_paths(r"\\localhost\a\b\c")  # Assumes this path is invalid on testing machine

System Information

$ python -m requests.help

{
  "chardet": {
    "version": "4.0.0"
  },
  "cryptography": {
    "version": "3.4.7"
  },
  "idna": {
    "version": "2.10"
  },
  "implementation": {
    "name": "CPython",
    "version": "3.8.10"
  },
  "platform": {
    "release": "10",
    "system": "Windows"
  },
  "pyOpenSSL": {
    "openssl_version": "101010bf",
    "version": "20.0.1"
  },
  "requests": {
    "version": "2.25.1"
  },
  "system_ssl": {
    "version": "101010bf"
  },
  "urllib3": {
    "version": "1.26.4"
  },
  "using_pyopenssl": true
}

This command is only available on Requests v2.16.4 and greater. Otherwise,
please provide some basic information about your system (Python version,
operating system, &c).

[tl-hbk]

This code path is only hit when using a patched certifi package that has certifi.where() return a UNC path