error when echo a rostopic when using gazebo_ros package for ros intergration approach.

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Hello,

I am using the gazeboros packages to build my program with catkin packages and I am publishing two topics one of them I used sensormsgs::LaserScan , the other topic I built its message that the problem happen with. The problem is when I use "rostopic echo " on a topic that I built, I get the following error :

ERROR: Cannot load message class for [angen_gazebo/PirMsg]. Are your messages built?

I dont have a problem using a "rostopic info" in which I get the information of this topic. Also I can use “rosmsg show” and “rostopic info” to get the information of the topic.

Meanwhile there is another topic that I publish and am using sensor_msgs::LaserScan type and I can echo its topic without any problem as the previous one. Note: both topics showed when using rostopic list

Can anyone help me plz! thanks in advance.