Declare test dependencies in [test] extra (ros-infrastructure#881)

Also make the 'mock' dependency conditional, now that this package
supports using unittest.mock.

.github/workflows/ci.yaml

@@ -27,10 +27,7 @@ jobs:
           python-version: ${{matrix.python}}
       - name: Install dependencies
         run: |
-          python -m pip install --upgrade pip setuptools
-          python -m pip install PyYAML argparse rospkg vcstools catkin_pkg python-dateutil rosdistro
-          python -m pip install -e .
-          python -m pip install pytest pytest-cov flake8 flake8-comprehensions mock codecov
+          python -m pip install -U -e .[test] codecov pytest-cov
       - name: Run tests
         run: |
           python -m pytest test --cov

setup.py

@@ -10,7 +10,14 @@
     'packages': ['rosdep2', 'rosdep2.ament_packages', 'rosdep2.platforms'],
     'package_dir': {'': 'src'},
     'install_requires': ['catkin_pkg >= 0.4.0', 'rospkg >= 1.4.0', 'rosdistro >= 0.7.5', 'PyYAML >= 3.1', 'setuptools'],
-    'test_requires': ['mock', 'pytest'],
+    'extras_require': {
+        'test': [
+            'flake8',
+            'flake8-comprehensions',
+            "mock; python_version < '3.3'",
+            'pytest',
+        ],
+    },
     'author': 'Tully Foote, Ken Conley',
     'author_email': '[email protected]',
     'maintainer': 'ROS Infrastructure Team',