Ebuild continues to generate despite dependency resolution failures

[allenh1]

Not sure when this was introduced, but there's an issue here.

$ superflore-gen-ebuilds --ros-distro melodic --only urdfdom_py
>>>> "melodic" distro detected...
>>>> Working in temporary directory /tmp/tmpjnx3nh8c
>>>> Creating new branch gentoo-bot-TxxAPJtePp...
>>>>
>>>> Regenerating package 'urdfdom_py'...
!!!! Failed to resolve required dependencies for package urdfdom_py!
!!!!  unresolved: "python3-lxml"
>>>> Pulling docker image 'allenh1/ros_gentoo_base:latest'...
>>>> Running docker image...
>>>> Generating manifests...
>>>> Working in temporary directory /tmp/tmp7vil5sbm
>>>> Running container with command string 'bash -c 'cd /tmp/ros-overlay/ros-melodic/urdfdom_py &>> /tmp/tmp7vil5sbm/log.txt && repoman manifest &>> /tmp/tmp7vil5sbm/log.txt''...
>>>> Docker container exited.
>>>> Cleaning up temporary directory /tmp/tmp7vil5sbm
>>>> Adding changes...
>>>> Committing to branch gentoo-bot-TxxAPJtePp...
>>>> Forking repository if a fork does not exist...
>>>> Pushing changes to fork...
>>>> Filing pull-request...
>>>> Successfully filed a pull request.
>>>>   https://github.com/ros/ros-overlay/pull/889
>>>> Successfully synchronized repositories!
>>>> Cleaning up temporary directory /tmp/tmpjnx3nh8c