Use setuptools<68 for Python 3.7

Author: Pavel Minaev

azure-pipelines/templates/run_tests.yml

@@ -2,6 +2,13 @@ steps:
   - script: "python -m pip install tox"
     displayName: "Setup Python packages"
 
+  # tox will automatically install the most recent version of setuptools to build the package.
+  # However, for Python 3.7, we want an older version of setuptools to avoid DeprecationWarning
+  # for pkg_resources getting triggered by test_gevent.
+  - script: 'python -m pip install "setuptools<68"'
+    displayName: "Install setuptools"
+    condition: "'$(python.version)' == '3.7'"
+
   - pwsh: |
       $toxEnv = '$(python.version)'
       if (-not $toxEnv.startsWith('pypy')) {