Add urllib3 to test matrix

This should fail for urllib3 v2 and pass for v1, since no changes have been made to the actual source code yet, and v2 should be incompatible. First stop on the way to fully fixing #116.

.circleci/config.yml

@@ -6,6 +6,9 @@ commands:
     parameters:
       python-version:
         type: string
+      urllib3-version:
+        type: string
+        default: "1"
       install-dev:
         description: Install dev dependencies (not just test dependencies)
         type: boolean
@@ -31,6 +34,7 @@ commands:
             pip install --upgrade pip
             pip install .
             pip install -r requirements-test.txt  # Extra requirements for tests.
+            pip install urllib3~=<< parameters.urllib3-version >>
 
       # Dev dependencies are only compatible on Python 3.8+, so only install
       # them on demand.
@@ -62,6 +66,8 @@ jobs:
     parameters:
       python-version:
         type: string
+      urllib3-version:
+        type: string
 
     working_directory: ~/wayback
     docker:
@@ -186,6 +192,11 @@ workflows:
           matrix:
             parameters:
               python-version: ["3.6", "3.7", "3.8", "3.9", "3.10", "3.11"]
+              urllib3-version: ["1", "2"]
+            exclude:
+              # urllib3v2 is not compatible with Python < 3.7.
+              - python-version: "3.6"
+                urllib3-version: "2"
       - test-python-prerelease
       - lint
       - build

requirements.txt

@@ -1,2 +1,2 @@
 requests
-urllib3 >=1.20, <2
+urllib3 >=1.20