Including another robot part via xacro

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Hi, I've been trying to attach a gripper to my manipulator and I've decided it would be best for my project if it was in another file. The problem is that I can't seem to do this correctly, when running the gazebo simulation I get the message

Error [parser_urdf.cc:3474] Unable to call parseURDF on robot model
Error [parser.cc:342] parse as old deprecated model file failed.
[INFO] [1511876200.859116, 10.141000]: Spawn status: SpawnModel: Entity pushed to spawn queue, but spawn service timed out waiting for entity to appear in simulation under the name Kuka_kr3

And the robot will not spawn. Below I attach the codes for robot and gripper. Another question that I have, is that I've made these files in similar fashion, but I don't know if I can use the macros defined in the manipulator file in gripper definition? So far, I've written it as a standard urdf file.

Manipulator file

<?xml version="1.0" ?>
<robot name="Kuka_kr3" xmlns:xacro="http://www.ros.org/wiki/xacro" >
  <gazebo>
    <plugin name="gazebo_ros_control" filename="libgazebo_ros_control.so">
      <robotNamespace>/kuka_kr3</robotNamespace>
    </plugin>
  </gazebo>

  <xacro:include filename="gripper.urdf.xacro" ns="gripper"/>

  <xacro:macro name="gazebo_reference" params="link_name color">
    <gazebo reference="${link_name}">
      <mu1>0.5</mu1>
      <mu2>0.5</mu2>
      <material>Gazebo/${color}</material>
    </gazebo>
  </xacro:macro>

  <xacro:gazebo_reference link_name="link0" color="Yellow"/>
  <xacro:gazebo_reference link_name="link1" color="Orange"/>
  <xacro:gazebo_reference link_name="link2" color="White"/>
  <xacro:gazebo_reference link_name="link3" color="Orange"/>
  <xacro:gazebo_reference link_name="link4" color="White"/>
  <xacro:gazebo_reference link_name="link5" color="Blue"/>
  <xacro:gazebo_reference link_name="link6" color="Red"/>

  <xacro:macro name="robot_joint" params="name type parent child *origin *axis effort_limit lower_effort_limit 
                                          upper_effort_limit transmission_name actuator_name">
    <joint name="${name}" type="${type}">
    <parent link="${parent}"/>
    <child link="${child}"/>
    <xacro:insert_block name="origin"/>
    <xacro:insert_block name="axis"/>
    <limit effort="${effort_limit}" lower="${lower_effort_limit}" upper="${upper_effort_limit}" velocity="1.0"/>
    <dynamics damping="0.2"/>
  </joint>
  <transmission name="${transmission_name}">
    <type>transmission_interface/SimpleTransmission</type>
    <joint name="${name}">
      <hardwareInterface>hardware_interface/EffortJointInterface</hardwareInterface>
    </joint>
    <actuator name="${actuator_name}">
      <hardwareInterface>EffortJointInterface</hardwareInterface>
      <mechanicalReduction>1</mechanicalReduction>
    </actuator>
  </transmission>
  </xacro:macro>

  <joint name="dummy" type="fixed">
    <parent link="dummy"/>
    <child link="link0"/>
    <origin rpy="0  0  0" xyz="0   0   0"/>
    <axis xyz="0  0  0"/>
    <limit effort="1.0" lower="-2.96705973" upper="2.96705973" velocity="1.0"/>
  </joint>

  <xacro:robot_joint name="joint0" 
                     type="revolute" parent="link0" child="link1" 
                     effort_limit="1.0" lower_effort_limit="-2.96705973" 
                     upper_effort_limit="2.96705973" transmission_name="trans0" 
                     actuator_name="motor0">
    <origin rpy="0  0  0" xyz="0   0   0.2"/>
    <axis xyz="0  0  1"/>
  </xacro:robot_joint>

  <xacro:robot_joint name="joint1" 
                     type="revolute" parent="link1" child="link2" 
                     effort_limit="500.0" lower_effort_limit="-1.3962634" 
                     upper_effort_limit="2.44346095" transmission_name="trans1" 
                     actuator_name="motor1">
    <origin rpy="0  0  0" xyz="0.02    0    0.15"/>
    <axis xyz="0  1  0"/>
  </xacro:robot_joint>

  <xacro:robot_joint name="joint2" 
                     type="revolute" parent="link2" child="link3" 
                     effort_limit="500.0" lower_effort_limit="-1.91986218" 
                     upper_effort_limit="2.70526034" transmission_name="trans2" 
                     actuator_name="motor2">
    <origin rpy="0  0  0" xyz="0     0     0.265"/>
    <axis xyz="0  1 ...