安装依赖项的时候有些问题

[Paulharden1]

ERROR: the following packages/stacks could not have their rosdep keys resolved
to system dependencies:
gazebo_state_plugins: No definition of [gazebo] for OS version [xenial]
gazebo_test_tools: No definition of [gazebo] for OS version [xenial]
gazebo_world_plugin_loader: No definition of [gazebo] for OS version [xenial]
robot_sim: Cannot locate rosdep definition for [moveit_ros]
gazebo_grasp_plugin: No definition of [gazebo] for OS version [xenial]
ur_driver: No definition of [python-lxml] for OS version [xenial]