How do you install a rosdep dependency under catkin/groovy?

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I've added these lines to foo/package.xml

<build_depend>mylib</build_depend>
<run_depend>mylib</run_depend>

and this to foo/CMakeLists.txt:

find_package(catkin REQUIRED COMPONENTS mylib)

and I added this rule to my local rosdep yaml file:

mylib:
  arch: mylib-syspkg

but when I run rosdep keys foo, I get a blank line, and if I try rosdep install foo, I get "#All required rosdeps installed successfully". A rosdep resolve mylib call prints out "mylib-syspkg".

If I run catkin_make:

CMake Error at /opt/ros/groovy/share/catkin/cmake/catkinConfig.cmake:71 (find_package):
  Could not find a package configuration file provided by "mylib" with any of
  the following names:

    mylibConfig.cmake
    mylib-config.cmake

It looks as if nothing is associating the mylib dependency with the foo package. Is there some new command I should run to install a wet package's rosdep dependencies?