This robot has a joint named "foo" which is not in the gazebo model.

edit

I know this question exists already but it doesn't help. I want to spawn a robot from urdf using the gazebo_ros package. I noticed that this happens whenever I define a link in my urdf with no additional parameters. for example in my case:

This robot has a joint named "pusher_joint" which is not in the gazebo model.

Where

<link name="pusher_base"/>

  <joint name="base_to_pusher" type="fixed">
      <parent link="base_link"/>
      <child link="pusher_base"/>
      <origin xyz="0.74 -1.058 0.18" rpy="0.000 -0.000 ${pi -1.045}"/> 
  </joint>

 <joint name="pusher_joint" type="prismatic">
     <axis xyz="-1 0 0" />
      <limit effort="20" velocity="10"  lower="0" upper="1.5"/>
      <parent link="pusher_base"/>
      <child link="pusher_end_effector"/>
      <origin xyz="0.0 0.0 0.0" rpy="0 0 0"/>
  </joint>

How can I fix this?