skj@laptop:~/Documents/snap/TK1$ sudo ubuntu-image -c edge  --extra-snaps /home/skj/Documents/snap/TK1/tk1_16-0.1_armhf.snap --extra-snaps /home/skj/Documents/snap/TK1/linux-generic-bbb_4.4.0-93-1.1_armhf.snap /home/skj/Documents/snap/TK1/tk1.model
[sudo] password for skj:
Fetching core
Copying "/home/skj/Documents/snap/TK1/linux-generic-bbb_4.4.0-93-1.1_armhf.snap" (linux-generic-bbb)
Copying "/home/skj/Documents/snap/TK1/tk1_16-0.1_armhf.snap" (tk1)
tk1 already prepared, skipping
linux-generic-bbb already prepared, skipping
WARNING: "linux-generic-bbb", "tk1" were installed from local snaps disconnected from a store and cannot be refreshed subsequently!
panic: runtime error: slice bounds out of range [recovered]
	panic: runtime error: slice bounds out of range

goroutine 1 [running]:
panic(0x5594d68fafa0, 0xc8200100c0)
	/usr/lib/go-1.6/src/runtime/panic.go:481 +0x3ea
main.main.func1()
	/build/snapd-44qGW9/snapd-2.28.1/_build/src/github.com/snapcore/snapd/cmd/snap/main.go:287 +0x7b
panic(0x5594d68fafa0, 0xc8200100c0)
	/usr/lib/go-1.6/src/runtime/panic.go:443 +0x4ed
github.com/snapcore/snapd/partition/ubootenv.OpenWithFlags(0xc8202f9580, 0x32, 0x1, 0x0, 0x0, 0x0)
	/build/snapd-44qGW9/snapd-2.28.1/_build/src/github.com/snapcore/snapd/partition/ubootenv/env.go:112 +0x65c
github.com/snapcore/snapd/partition.(*uboot).SetBootVars(0x5594d6d1af18, 0xc820341590, 0x0, 0x0)
	/build/snapd-44qGW9/snapd-2.28.1/_build/src/github.com/snapcore/snapd/partition/uboot.go:59 +0x75
github.com/snapcore/snapd/image.setBootvars(0xc8202fca50, 0x0, 0x0)
	/build/snapd-44qGW9/snapd-2.28.1/_build/src/github.com/snapcore/snapd/image/image.go:483 +0x55a
github.com/snapcore/snapd/image.bootstrapToRootDir(0xc820173c20, 0xc8200c2840, 0xc8200bb8f0, 0xc820360120, 0x0, 0x0)
	/build/snapd-44qGW9/snapd-2.28.1/_build/src/github.com/snapcore/snapd/image/image.go:433 +0x212a
github.com/snapcore/snapd/image.Prepare(0xc8200bb8f0, 0x0, 0x0)
	/build/snapd-44qGW9/snapd-2.28.1/_build/src/github.com/snapcore/snapd/image/image.go:154 +0x38d
main.(*cmdPrepareImage).Execute(0xc8200159a0, 0xc820192cc0, 0x0, 0x6, 0x0, 0x0)
	/build/snapd-44qGW9/snapd-2.28.1/_build/src/github.com/snapcore/snapd/cmd/snap/cmd_prepare_image.go:72 +0x22f
github.com/snapcore/snapd/vendor/github.com/jessevdk/go-flags.(*Parser).ParseArgs(0xc82006b980, 0xc82000a0f0, 0x6, 0x6, 0x0, 0x0, 0x0, 0x0, 0x0)
	/build/snapd-44qGW9/snapd-2.28.1/_build/src/github.com/snapcore/snapd/vendor/github.com/jessevdk/go-flags/parser.go:316 +0xa85
github.com/snapcore/snapd/vendor/github.com/jessevdk/go-flags.(*Parser).Parse(0xc82006b980, 0x0, 0x0, 0x0, 0x0, 0x0)
	/build/snapd-44qGW9/snapd-2.28.1/_build/src/github.com/snapcore/snapd/vendor/github.com/jessevdk/go-flags/parser.go:186 +0x9d
main.run(0x0, 0x0)
	/build/snapd-44qGW9/snapd-2.28.1/_build/src/github.com/snapcore/snapd/cmd/snap/main.go:308 +0x4a
main.main()
	/build/snapd-44qGW9/snapd-2.28.1/_build/src/github.com/snapcore/snapd/cmd/snap/main.go:292 +0x834
COMMAND FAILED: snap prepare-image --channel=edge --extra-snaps=/home/skj/Documents/snap/TK1/tk1_16-0.1_armhf.snap --extra-snaps=/home/skj/Documents/snap/TK1/linux-generic-bbb_4.4.0-93-1.1_armhf.snap /home/skj/Documents/snap/TK1/tk1.model /tmp/tmpc6dtdvsk/unpack
skj@laptop:~/Documents/snap/TK1$ snap version
snap    2.28.1
snapd   2.28.1
series  16
ubuntu  16.04
kernel  4.10.0-35-generic