Costume world fail to load in Hector_quadrotor_gazeboo

edit

If you look at the source for the quadrotor_empty_world.launch you'll see that it doesn't have a world argument.

<?xml version="1.0"?>

<launch>
  <arg name="paused" default="false"/>
  <arg name="use_sim_time" default="true"/>
  <arg name="gui" default="true"/>
  <arg name="headless" default="false"/>
  <arg name="debug" default="false"/>

  <include file="$(find gazebo_ros)/launch/empty_world.launch">
    <arg name="paused" value="$(arg paused)"/>
    <arg name="use_sim_time" value="$(arg use_sim_time)"/>
    <arg name="gui" value="$(arg gui)"/>
    <arg name="headless" value="$(arg headless)"/>
    <arg name="debug" value="$(arg debug)"/>
  </include>

  <include file="$(find hector_quadrotor_gazebo)/launch/spawn_quadrotor.launch" />
</launch>

So, what you'll want to do is create a new launch file in your package that's similar to the one that you're using and include your custom world instead. You can make it a little more flexible by add a world argument that you're trying to use (let's call it world_name to be consistent with the empty_world.launch file):

<launch>
  <arg name="paused" default="false"/>
  <arg name="use_sim_time" default="true"/>
  <arg name="gui" default="true"/>
  <arg name="headless" default="false"/>
  <arg name="debug" default="false"/>
  <arg name="world_name"/>

  <include file="$(find gazebo_ros)/launch/empty_world.launch">
    <arg name="world_name" value="$(arg world_name)"/>
    <arg name="paused" value="$(arg paused)"/>
    <arg name="use_sim_time" value="$(arg use_sim_time)"/>
    <arg name="gui" value="$(arg gui)"/>
    <arg name="headless" value="$(arg headless)"/>
    <arg name="debug" value="$(arg debug)"/>
  </include>

  <include file="$(find hector_quadrotor_gazebo)/launch/spawn_quadrotor.launch" />
</launch>

Now, you should be able use it similarly to how you're currently trying to use it:

roslaunch my_package my_world.launch world_name:=2.world

One caveat is indicted in the empty_world.launch file

the world_name is with respect to GAZEBO_RESOURCE_PATH environmental variable

so you might have to work that out. Hopefully, this at least gives you something to go off of.

Update:

From the Gazebo tutorials,

GAZEBO_RESOURCE_PATH: colon-separated set of directories where Gazebo will search for other resources such as world and media files.