Bug: Remove reliance on usrmerge diversions

[orndorffgrant]

Description of the bug

ubuntu-pro-client ships systemd units to /libon all releases, which are then diverted to /usr/lib on focal onward.

Expected behavior

ubuntu-pro-client should ship systemd units to the correct location per ubuntu release. /lib on bionic and earlier, /usr/lib on focal and later.

Current behavior

ubuntu-pro-client ships systemd units to /lib on all releases, which are then diverted to /usr/lib on focal onward.

To Reproduce

dpkg -L will show the diversion on any ubuntu machine focal onward

System information:

• Ubuntu release: focal onward
• Pro Client version: 34

Additional context

At least on xenial, the units need to be delivered to /lib - if they are put in /usr/lib, then they won't be correctly enabled and started.

[dheyay]

The current issue arises because the debian helper version we are using doesn't properly handle systemd files in the /usr/lib/ directory. Instead, it looks for files in the outdated /lib/ directory. Fixing this might require a re-write of the debian/rules using a newer debian helper version.

Reference: https://github.com/Debian/debhelper/blob/master/dh_systemd_enable

Short fix tried to resolve the issue was:

In debian/rules:
Changes take into account we still use the /usr/lib focal onwards

ifneq (${VERSION_ID},"16.04")
	# Only install cloud-id-shim on Xenial
-       rm $(CURDIR)/debian/ubuntu-pro-client/lib/systemd/system/ubuntu-advantage-cloud-id-shim.service
+	ifeq (${VERSION_ID},"18.04")
+		# If on bionic, remove from /lib/
+		rm $(CURDIR)/debian/ubuntu-pro-client/lib/systemd/system/ubuntu-advantage-cloud-id-shim.service
+	else
+		# For other versions, remove from usr/lib/
+		rm $(CURDIR)/debian/ubuntu-pro-client/usr/lib/systemd/system/ubuntu-advantage-cloud-id-shim.service
+	endif
endif

	# Move ua-auto-attach.service out to ubuntu-pro-auto-attach
-	mkdir -p debian/ubuntu-pro-auto-attach/lib/systemd/system
-	mv debian/ubuntu-pro-client/lib/systemd/system/ua-auto-attach.* debian/ubuntu-pro-auto-attach/lib/systemd/system
+	if [ "${VERSION_ID}" = "16.04" ] || [ "${VERSION_ID}" = "18.04" ]; then
+		mkdir -p debian/ubuntu-pro-auto-attach/lib/systemd/system
+		mv debian/ubuntu-pro-client/lib/systemd/system/ua-auto-attach.* debian/ubuntu-pro-auto-attach/lib/systemd/system
+	else
+		mkdir -p debian/ubuntu-pro-auto-attach/usr/lib/systemd/system
+		mv debian/ubuntu-pro-client/usr/lib/systemd/system/ua-auto-attach.* debian/ubuntu-pro-auto-attach/usr/lib/systemd/system
+	fi

And in setup.py:
To re-direct the files to the correct directory based on release

def _get_data_files():
+    series = system.get_release_info().series
+    if series == "xenial":
+        systemd_files = ("/lib/systemd/system", glob.glob("systemd/*"))
+    else:
+        systemd_files =  ("/usr/lib/systemd/system", glob.glob("systemd/*"))
    return [
        ("/etc/ubuntu-advantage", ["uaclient.conf"]),
        ("/etc/update-motd.d", glob.glob("update-motd.d/*")),
        ("/usr/lib/ubuntu-advantage", glob.glob("lib/[!_]*")),
        ("/usr/share/keyrings", glob.glob("keyrings/*")),
        (
            "/etc/update-manager/release-upgrades.d/",
            ["release-upgrades.d/ubuntu-advantage-upgrades.cfg"],
        ),
        ("/etc/apt/preferences.d", glob.glob("preferences.d/*")),
        (defaults.CONFIG_DEFAULTS["data_dir"], []),
-        ("/lib/systemd/system", glob.glob("systemd/*")),
+       systemd_files,
        (
            "/usr/share/apport/package-hooks",
            ["apport/source_ubuntu-advantage-tools.py"],
        ),
    ]