[PR #5557/bb4ee18d backport][3.8] test_proxy_from_env did not clear proxies already set in the

[webknjaz]

This is a backport of PR #5557 as merged into master (bb4ee18).

environment. Added code to first clear proxies that were already set.

Refactored the parametrize input on test_proxy_from_env to work more like test_get_env_proxy_for_url to be consistent.

(cherry picked from commit bb4ee18)

What do these changes do?

Fix failing tests when a environment proxy is set.

test_proxy_from_env did not clear proxies already set in the environment. Added code to first clear proxies that were already set.

Refactored the parametrize input on test_proxy_from_env to work more like test_get_env_proxy_for_url to be consistent.

Are there changes in behavior for the user?

No.

Related issue number

#5554

Checklist

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