Ubuntu18.04 Melodic
执行这条命令后，有如下报错
[INFO] [1673777588.618213, 1814.801000]: Spawn status: SpawnModel: Entity pushed to spawn queue, but spawn service timed out waiting for entity to appear in simulation under the name iris_0
[ERROR] [1673777588.619052, 1814.801000]: Spawn service failed. Exiting.
Warning [parser.cc:833] XML Attribute[version] in element[sdf] not defined in SDF, ignoring.
Exception in thread Thread-5 (most likely raised during interpreter shutdown):
Traceback (most recent call last):
File "/usr/lib/python2.7/threading.py", line 801, in __bootstrap_inner
File "/usr/lib/python2.7/threading.py", line 754, in run
File "/usr/lib/python2.7/SocketServer.py", line 603, in process_request_thread
File "/usr/lib/python2.7/SocketServer.py", line 475, in shutdown_request
<type 'exceptions.AttributeError'>: 'NoneType' object has no attribute 'error'
[iris_0/iris_0_spawn-5] process has died [pid 28017, exit code 1, cmd /home/lad/catkin_ws/src/gazebo_ros_pkgs/gazebo_ros/scripts/spawn_model -sdf -param model_description -model iris_0 -x 0 -y 7.5 -z 0.5 -R 0 -P 0 -Y 0 __name:=iris_0_spawn __log:=/home/lad/.ros/log/33eb3ef2-94bd-11ed-b8dc-08002717c910/iris_0-iris_0_spawn-5.log].
log file: /home/lad/.ros/log/33eb3ef2-94bd-11ed-b8dc-08002717c910/iris_0-iris_0_spawn-5*.log
Warning [parser.cc:833] XML Attribute[version] in element[sdf] not defined in SDF, ignoring.
Warning [parser.cc:833] XML Attribute[version] in element[sdf] not defined in SDF, ignoring.
Warning [parser.cc:833] XML Attribute[version] in element[sdf] not defined in SDF, ignoring.
跟着教程执行了一系列命令后也没有出现下图中的内容
请问我该怎么解决这些问题
