remove unused imports and add comments for catkin test results workar…

…ound

catkin_tools/jobs/catkin.py

@@ -12,9 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import csv
 import os
-import threading
 
 
 from catkin_tools.argument_parsing import handle_make_arguments
@@ -30,10 +28,7 @@
 from .commands.cmake import CMakeMakeIOBufferProtocol
 from .commands.make import MAKE_EXEC
 
-from .job import create_env_file
-from .job import get_env_file_path
 from .job import get_env_loader
-from .job import get_package_build_space_path
 from .job import makedirs
 
 
@@ -45,6 +40,7 @@
 
 
 def ctr_nuke(logger, event_queue, prefix):
+    """Adds a shell script which clears the catkin and ros test results dir."""
     ctr_nuke_path = os.path.join(prefix, 'etc', 'catkin', 'profile.d')
     ctr_nuke_filename = os.path.join(ctr_nuke_path, '06-ctr-nuke.sh')
     mkdir_p(ctr_nuke_path)
@@ -80,6 +76,10 @@ def create_catkin_build_job(context, package, package_path, dependencies, force_
 
     # Define test results directory
     catkin_test_results_dir = os.path.join(build_space, 'test_results')
+    # Always override the CATKIN and ROS _TEST_RESULTS_DIR environment variables.
+    # This is in order to avoid cross talk due to parallel builds.
+    # This is only needed for ROS Hydro and earlier (the problem was addressed upstream in Indigo).
+    # See: https://github.com/catkin/catkin_tools/issues/139
     ctr_env = {
         'CATKIN_TEST_RESULTS_DIR': catkin_test_results_dir,
         'ROS_TEST_RESULTS_DIR': catkin_test_results_dir
@@ -88,6 +88,7 @@ def create_catkin_build_job(context, package, package_path, dependencies, force_
     # Construct CMake command
     makefile_path = os.path.join(build_space, 'Makefile')
     if not os.path.isfile(makefile_path) or force_cmake:
+        # Create a shell script which clears the catkin and ros test results environment variable.
         stages.append(FunctionStage(
             'ctr-nuke',
             ctr_nuke,