Pin pyparsing to 2.4.7. (#602)
Pin pyparsing to 2.4.7. (#602)

This is currently recommended by the upstream maintainers.

Signed-off-by: Chris Lalancette <281cd07d7578d97c83271fbbf2faddb83ab3791c@openrobotics.org>
ros2/ci,ros2/ci,ros2/ci