RHEL 6 is also affected.

+++ This bug was initially created as a clone of Bug #1596494 +++

Description of problem:
The RHUI plug-in for sos reads:

    rhui_debug_path = "/usr/share/rh-rhua/rhui-debug.py"
...
        if self.is_installed("pulp-cds"):
            cds = "--cds"
        else:
            cds = ""

        rhui_debug_dst_path = self.get_cmd_output_path()
        self.add_cmd_output(
            "python %s %s --dir %s"
            % (self.rhui_debug_path, cds, rhui_debug_dst_path),
            suggest_filename="rhui-debug")

The way the script decides whether it's running on a CDS node (as opposed to a RHUA node) worked on RHUI 2, where pulp-cds was indeed a valid package name, but  on RHUI 3 there's no such package. Consequently, the rhui-debug script is executed without --cds and doesn't collect the right config and log files that are present on a CDS node. In fact, no useful data is collected as the files that are collected in the "non-CDS" mode only exist on RHUA nodes.

RHUI 2 is no longer supported (see https://access.redhat.com/support/policy/updates/rhui for the schedule), so it should be safe to change the detection in a way that's not backward compatible with RHUI 2. As for how the detection should be made, there isn't any package specific to CDS nodes, but perhaps you could check if the /etc/httpd/conf.d/03-crane.conf file exists, as it only exists on CDSes. So the implementation could be as follows:

import os
...
        if os.path.isfile("/etc/httpd/conf.d/03-crane.conf"):
            cds = "--cds"
        else:
            cds = ""

I've checked this and it works well.

Version-Release number of selected component (if applicable):
sos-3.5-9.el7_5

How reproducible:
Always

Steps to Reproduce:
1. install sos on a RHUI CDS node
2. until bug 1596296 is fixed, manually create /usr/share/rh-rhua/rhui-debug.py
3. run sosreport -o rhui

Actual results:
The tarball doesn't contain anything useful

Expected results:
The tarball contains CDS-specific files, for example:
etc/httpd/conf.d/25-cds.example.com.conf
var/log/httpd/cds.example.com_access_ssl.log