> You should skip the key when invoking rosdep (--skip-keys) and install the package manually via pip.
--skip-keys was part of the command:
rosdep install --from-paths src --ignore-src --rosdistro dashing -y --skip-keys "console_bridge fastcdr fastrtps libopensplice67 libopensplice69 rti-connext-dds-5.3.1 urdfdom_headers"
Now I do see from pip it's already installed with Python 3.8:
Requirement already satisfied: pep8 in /usr/local/lib/python3.8/site-packages (1.7.1)
So that's the Fedora Python. We also have Anaconda Python 3.7 and pep8 is there as well:
/usr/local/bin/anaconda3/bin/python -m pip install pep8
Requirement already satisfied: pep8 in /usr/local/bin/anaconda3/lib/python3.7/site-packages (1.7.1)
> Note that this is only a problem for Eloquent and older. In Foxy, I converted the package to use pycodestyle directly.
I tried with foxy, same error:
rosdep install --from-paths src --ignore-src --rosdistro foxy -y --skip-keys "console_bridge fastcdr fastrtps libopensplice67 libopensplice69 rti-connext-dds-5.3.1 urdfdom_headers"
ERROR: the following packages/stacks could not have their rosdep keys resolved
to system dependencies:
ament_pep8: No definition of [python3-pep8] for OS version 
Thanks for the reply Scott, I'm feeling more hopeful. Could it be a Python version issues, e.g., Fedora's Python vs Anaconda Python?
BTW, are questions about Gazebo allowed? Using X2Go it segfaults and I posted that here: https://bugs.launchpad.net/sr-ros-interface/+bug/1891654