Could not find a configuration file for package *

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Here's a minimal catkin package.

Package.xml:

<?xml version="1.0"?>
<package>
  <name>sighdangitcatkin</name>
  <version>0.0.0</version>
  <description>The sighdangitcatkin package</description>
  <maintainer <a href="mailto:email="dlu@todo.todo">dlu</maintainer">email="dlu@todo.todo">dlu</maintainer</a>>
  <license>TODO</license>
  <buildtool_depend>catkin</buildtool_depend>
  <build_depend>orocos_kdl</build_depend>
</package>

CMakeLists.txt:

cmake_minimum_required(VERSION 2.8.3)
project(sighdangitcatkin)

find_package(catkin REQUIRED COMPONENTS orocos_kdl )
catkin_package()

Seems pretty simple, yah? Here's the error I get when compiling.

-- +++ processing catkin package: 'sighdangitcatkin'
-- ==> add_subdirectory(sighdangitcatkin)
CMake Error at /opt/ros/hydro/share/catkin/cmake/catkinConfig.cmake:72 (find_package):
  Could not find a configuration file for package orocos_kdl.

  Set orocos_kdl_DIR to the directory containing a CMake configuration file
  for orocos_kdl.  The file will have one of the following names:

    orocos_kdlConfig.cmake
    orocos_kdl-config.cmake

Call Stack (most recent call first):
  sighdangitcatkin/CMakeLists.txt:4 (find_package)


-- Configuring incomplete, errors occurred!
Invoking "cmake" failed

What am I missing?

Note: It works fine if you use this CMake..

 cmake_minimum_required(VERSION 2.8.3)
 project(sighdangitcatkin)
 find_package(catkin REQUIRED COMPONENTS )
 find_package(orocos_kdl REQUIRED)
 catkin_package()