I'm trying to restore android after playing around with ubuntu touch

I follow exactly the same steps described the ubuntu's wiki page i.e.

1. Download the factory image corresponding to your device's model and
   version (initial table has links).




2. Ensure the device is connected and powered on.




3. Extract the downloaded file and cd into the extracted directory.




4. run adb reboot-bootloader




5. run ./flash-all.sh (use sudo if lack of permissions on the
   workstation don't allow you to talk to the device).

The archive is downloaded successfully, checked the sha1 checksum everything is ok.
But the ./flash-all.sh fails like this

sending 'bootloader' (2308 KB)...

OKAY [  0.513s]

writing 'bootloader'...

OKAY [  0.292s]

finished. total time: 0.805s

rebooting into bootloader...

OKAY [  0.007s]

finished. total time: 0.008s

sending 'radio' (12288 KB)...

OKAY [  2.668s]

writing 'radio'...

OKAY [  1.372s]

finished. total time: 4.040s

rebooting into bootloader...

OKAY [  0.009s]

finished. total time: 0.009s

archive does not contain 'boot.sig'

archive does not contain 'recovery.sig'

failed to allocate 435793780 bytes

error: update package missing system.img

My device is Nexus 4. Tried both 4.2.2 and 4.3 androind versions for Nexus 4 still the same.
Any ideas how problem can be solved ?