Test on urllib3 1.26.x

[nateprewitt]

First step to address #6734. We'll enable testing on urllib3 1.26.x which was lost when we moved the pin to support 2.x. These will fail for now until the underlying issue is addressed, but this is to ensure we're catching any future breakages.

[sethmlarson]

LGTM! Thanks for testing urllib3 :)

[sethmlarson]

I believe this is a string, not an integer. Also, should do a >= check instead of equals.

[nateprewitt]

Good catch on the int. For the equivalence, I don't know if >= is what we want if this is specifically scoping the 2.x major version. In the same way I wouldn't want an is_py3 to include Python 4.x. We could do something like is_gt_urllib3_1 but that seems like it may be premature forwards-compatibility?

Right now our dependencies are scoped at urllib3<3 and if we add this check to any other behaviors, I'd rather they stay scoped to the major version. That will let tests fail if we major version again and we can make an informed decision at that point when adding support. Otherwise, we may unintentionally carry forward behaviors that are subtly wrong.

I can see similar risks with both sides, so not a hill I'm going to die on, but that was my initial thought process.

[nateprewitt]

I've changed the check from checking for urllib3 2.x to check for 1.x. That leaves us open to forward compatibility without the confusing behavior with is_urllib3_2 including newer major versions.