Update test_flake8.py files

Signed-off-by: Christophe Bedard <bedard.christophe@gmail.com>

ros2trace_analysis/test/test_flake8.py

@@ -12,12 +12,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from ament_flake8.main import main
+from ament_flake8.main import main_with_errors
 import pytest
 
 
 @pytest.mark.flake8
 @pytest.mark.linter
 def test_flake8():
-    rc = main(argv=[])
-    assert rc == 0, 'Found errors'
+    rc, errors = main_with_errors(argv=[])
+    assert rc == 0, \
+        'Found %d code style errors / warnings:\n' % len(errors) + \
+        '\n'.join(errors)