How do I mark pip-installed dependencies as satisfied?

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I've been trying to get ROS Hydro to run on Arch Linux, which uses Python 3 by default, and pacman for package management.

I've fixed a few Python 2/3 issues with rosdep, rospkg, etc, which I installed via pip. I've reached the step of running rosdep for the catkin workspace. My command is:

rosdep install --from-paths src --ignore-src --rosdistro hydro -y

This gives me a bunch of errors like:

rqt_publisher: No definition of [python-rospkg] for OS [arch]
rqt_top: No definition of [python-psutil] for OS [arch]
pcl_ros: No definition of [libpcl-all] for OS [arch]
rosclean: No definition of [python-rospkg] for OS [arch]
smach_ros: No definition of [python-rosdep] for OS [arch]
...

Looking at the arch dependencies, there doesn't appear to be some packages defined for Arch: github.com/ros/rosdistro/blob/master/rosdep/python.yaml

Since I didn't install using pacman (which is set up as the Arch package manager), what's the best way to tell rosdep that I've satisfied dependencies with pip?