Add a test dependency on pytest. (#45)

While there aren't currently tests defined here, this sets it up so that
it is ready for pytest tests.

package.xml

@@ -18,15 +18,12 @@
   <exec_depend>ament_index_python</exec_depend>
   <exec_depend version_gte="0.2.19">python_qt_binding</exec_depend>
   <exec_depend>rclpy</exec_depend>
+  <exec_depend>rcl_interfaces</exec_depend>
   <exec_depend>rqt_gui</exec_depend>
   <exec_depend>rqt_gui_py</exec_depend>
   <exec_depend>rqt_py_common</exec_depend>
 
-  <!-- TODO(mlautman): Replace once rqt_logger_level has been ported -->
-  <!-- <exec_depend>rqt_logger_level</exec_depend> -->
-
-  <!-- Note: This is needed for rcl_interfaces Log.msg -->
-  <exec_depend>rcl_interfaces</exec_depend>
+  <test_depend>python3-pytest</test_depend>
 
   <export>
     <architecture_independent/>

setup.py

@@ -39,6 +39,7 @@
         'rqt_console provides a GUI plugin for displaying and filtering ROS messages.'
     ),
     license='BSD',
+    tests_require=['pytest'],
     entry_points={
         'console_scripts': [
             'rqt_console = ' + package_name + '.main:main',