fix: Python 3.8 support

.github/workflows/unittest.yml

@@ -0,0 +1,58 @@
+on:
+  pull_request:
+    branches:
+      - main
+name: unittest
+jobs:
+  unit:
+    runs-on: ubuntu-22.04
+    strategy:
+      matrix:
+        python: ['3.8']
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v4
+    - name: Setup Python
+      uses: actions/setup-python@v5
+      with:
+        python-version: ${{ matrix.python }}
+    - name: Install nox
+      run: |
+        python -m pip install --upgrade setuptools pip wheel
+        python -m pip install nox
+    - name: Run unit tests
+      env:
+        COVERAGE_FILE: .coverage-${{ matrix.python }}
+      run: |
+        nox -s unit-${{ matrix.python }}
+    - name: Upload coverage results
+      uses: actions/upload-artifact@v4
+      with:
+        name: coverage-artifact-${{ matrix.python }}
+        path: .coverage-${{ matrix.python }}
+        include-hidden-files: true
+
+  cover:
+    runs-on: ubuntu-latest
+    needs:
+        - unit
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v4
+    - name: Setup Python
+      uses: actions/setup-python@v5
+      with:
+        python-version: "3.13"
+    - name: Install coverage
+      run: |
+        python -m pip install --upgrade setuptools pip wheel
+        python -m pip install coverage
+    - name: Download coverage results
+      uses: actions/download-artifact@v4
+      with:
+        path: .coverage-results/
+    - name: Report coverage results
+      run: |
+        find .coverage-results -type f -name '*.zip' -exec unzip {} \;
+        coverage combine .coverage-results/**/.coverage*
+        coverage report --show-missing --fail-under=99

google/auth/_default.py

@@ -16,8 +16,9 @@
 
 Implements application default credentials and project ID detection.
 """
+from __future__ import annotations
 
-from collections.abc import Sequence
+from typing import Sequence
 import io
 import json
 import logging

google/oauth2/id_token.py

@@ -54,6 +54,7 @@
     http://openid.net/specs/openid-connect-core-1_0.html#IDToken
 .. _CacheControl: https://cachecontrol.readthedocs.io
 """
+from __future__ import annotations
 
 import http.client as http_client
 import json

noxfile.py

@@ -32,9 +32,7 @@
 ]
 
 DEFAULT_PYTHON_VERSION = "3.14"
-# TODO(https://github.com/googleapis/google-auth-library-python/issues/1787):
-# Remove or restore testing for Python 3.7/3.8
-UNIT_TEST_PYTHON_VERSIONS = ["3.9", "3.10", "3.11", "3.12", "3.13", "3.14"]
+UNIT_TEST_PYTHON_VERSIONS = ["3.7", "3.8", "3.9", "3.10", "3.11", "3.12", "3.13", "3.14"]
 
 # Error if a python version is missing
 nox.options.error_on_missing_interpreters = True
@@ -44,8 +42,6 @@
     "lint",
     "blacken",
     "mypy",
-    # TODO(https://github.com/googleapis/google-auth-library-python/issues/1787):
-    # Remove or restore testing for Python 3.7/3.8
     "unit-3.9",
     "unit-3.10",
     "unit-3.11",