Ubuntu – Failed to load modules at startup: Could not find module by name ‘off’

I just upgraded from 15.04 to 15.10 and during the boot process I now get an error saying that some modules failed to load. So I ran systemctl status -l systemd-modules-load.service and I got this:

Oct 24 12:22:23 ubuntu systemd-modules-load[292]: Inserted module 'option'
Oct 24 12:22:23 ubuntu systemd-modules-load[292]: could not find module by name='off'
Oct 24 12:22:23 ubuntu systemd-modules-load[292]: Failed to insert 'off': Function not implemented
Oct 24 12:22:23 ubuntu systemd-modules-load[292]: could not find module by name='off'
Oct 24 12:22:23 ubuntu systemd-modules-load[292]: Failed to insert 'off': Function not implemented
Oct 24 12:22:23 ubuntu systemd-modules-load[292]: Inserted module 'cuse'
Oct 24 12:22:23 ubuntu systemd[1]: systemd-modules-load.service: Main process exited, code=exited, status=1/FAILURE
Oct 24 12:22:23 ubuntu systemd[1]: Failed to start Load Kernel Modules.
Oct 24 12:22:23 ubuntu systemd[1]: systemd-modules-load.service: Unit entered failed state.
Oct 24 12:22:23 ubuntu systemd[1]: systemd-modules-load.service: Failed with result 'exit-code'.

When I run cat /etc/modules I get

loop
lp
usbserial
option
nouveau
nouveau

I tried to comment out one of the nouveau modules but it didn't help.

I found a bug on Launchpad which gives a similar message but my problem doesn't seem to be caused by the rtc module (which is the culprit in the linked bug).

Anyone has an idea what I should try?

EDIT: added more info:

cat /lib/systemd/system/systemd-modules-load.service gives

[Unit]
Description=Load Kernel Modules
Documentation=man:systemd-modules-load.service(8) man:modules-load.d(5)
DefaultDependencies=no
Conflicts=shutdown.target
Before=sysinit.target shutdown.target
ConditionCapability=CAP_SYS_MODULE
ConditionDirectoryNotEmpty=|/lib/modules-load.d
ConditionDirectoryNotEmpty=|/usr/lib/modules-load.d
ConditionDirectoryNotEmpty=|/usr/local/lib/modules-load.d
ConditionDirectoryNotEmpty=|/etc/modules-load.d
ConditionDirectoryNotEmpty=|/run/modules-load.d
ConditionKernelCommandLine=|modules-load
ConditionKernelCommandLine=|rd.modules-load

[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/lib/systemd/systemd-modules-load
TimeoutSec=90s

cat /etc/modules-load.d/modules.conf gives the same output as cat /etc/modules/ listed above.