Update launch test for change related to enviroment variables in launch (ros2#354)

Since ros2/launch#601, launch no longer modifies os.environ.
Rather, it updates a dictionary owned by the launch context, which is then passed to
launched executables.

Signed-off-by: Jacob Perron <jacob@openrobotics.org>

Author: jacobperron

test/test_logging_long_messages.py

@@ -17,6 +17,7 @@
 
 from launch import LaunchDescription
 from launch.actions import ExecuteProcess
+from launch.actions import SetEnvironmentVariable
 
 import launch_testing
 import launch_testing.actions
@@ -28,15 +29,20 @@
 def generate_test_description():
     launch_description = LaunchDescription()
     # Set the output format to a "verbose" format that is expected by the executable output
-    os.environ['RCUTILS_CONSOLE_OUTPUT_FORMAT'] = \
-        '[{severity}] [{name}]: {message} ({function_name}() at {file_name}:{line_number})'
+    launch_description.add_action(
+        SetEnvironmentVariable(
+            name='RCUTILS_CONSOLE_OUTPUT_FORMAT',
+            value='[{severity}] [{name}]: {message} '
+                  '({function_name}() at {file_name}:{line_number})'
+        )
+    )
     executable = os.path.join(os.getcwd(), 'test_logging_long_messages')
     if os.name == 'nt':
         executable += '.exe'
     process_name = 'test_logging_long_messages'
-    launch_description.add_action(ExecuteProcess(
-        cmd=[executable], name=process_name, output='screen'
-    ))
+    launch_description.add_action(
+        ExecuteProcess(cmd=[executable], name=process_name, output='screen')
+    )
 
     launch_description.add_action(
         launch_testing.actions.ReadyToTest()