I am attempting to install ROS Melodic on Ubuntu 18.04 following this help documentation: http://wiki.ros.org/melodic/Installation/Ubuntu

My installation is failing at the last step (1.7) where I enter the command:

sudo apt install python-rosinstall python-rosinstall-generator python-wstool build-essential

Below I will post the error that is output. Can you suggest what is going wrong and how I can fix it? Any advice would be extremely appreciated.

.... lines removed by OP for brevity
Unpacking subversion (1.9.7-4ubuntu1) ...
Selecting previously unselected package python-vcstools.
Preparing to unpack .../11-python-vcstools0.1.42-1all.deb ...
Unpacking python-vcstools (0.1.42-1) ...
Selecting previously unselected package python-wstool.
Preparing to unpack .../12-python-wstool0.1.17-1all.deb ...
Unpacking python-wstool (0.1.17-1) ...
Selecting previously unselected package python-rosinstall.
Preparing to unpack .../13-python-rosinstall0.7.8-1all.deb ...
Unpacking python-rosinstall (0.7.8-1) ...
Selecting previously unselected package python-rosinstall-generator.
Preparing to unpack .../14-python-rosinstall-generator0.1.16-1all.deb ...
Unpacking python-rosinstall-generator (0.1.16-1) ...
Errors were encountered while processing:
/tmp/apt-dpkg-install-qn5l0e/07-python-rospkg-modules1.1.10-1all.deb
/tmp/apt-dpkg-install-qn5l0e/08-python-rosdistro-modules0.7.4-1all.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)