Arch Linux

Description:
The unit file for ipp-usb, as presented below:

##### /usr/lib/systemd/system/ipp-usb.service #####
[Unit]
Description=Daemon for IPP over USB printer support
Documentation=man:ipp-usb(8)
After=cups.service avahi-daemon.service
Wants=avahi-daemon.service

[Service]
Type=oneshot
ExecStart=/sbin/ipp-usb udev
###################################################

is faulty.
On attempting to enable the service (as recommended per https://wiki.archlinux.org/index.php/SANE#Installation ):

###
[root@dustmite ~]# systemctl enable ipp-usb.service
The unit files have no installation config (WantedBy=, RequiredBy=, Also=,
Alias= settings in the [Install] section, and DefaultInstance= for template
units). This means they are not meant to be enabled using systemctl.

Possible reasons for having this kind of units are:
• A unit may be statically enabled by being symlinked from another unit's
.wants/ or .requires/ directory.
• A unit's purpose may be to act as a helper for some other unit which has
a requirement dependency on it.
• A unit may be started when needed via activation (socket, path, timer,
D-Bus, udev, scripted systemctl call, ...).
• In case of template units, the unit is meant to be enabled with some
instance name specified.
###

Additionally, it lists "cups.service" as an "After" requisite, yet there is no cups.service unit (perhaps this should use "org.cups.cupsd.service" in its place).

Additional info:
* package version(s): 0.9.10-1

Steps to reproduce:
See above.