Getting the exact same thing here too - Raspberry Pi3 - any ideas?
16 error Linux 4.4.34-v7+
17 error argv “/usr/local/bin/node” “/usr/local/bin/npm” “start”
18 error node v6.9.4
19 error npm v3.10.10
20 error file sh
21 error code ELIFECYCLE
22 error errno ENOENT
23 error syscall spawn
24 error magicmirror@2.1.0 start: electron js/electron.js
24 error spawn ENOENT
25 error Failed at the magicmirror@2.1.0 start script ‘electron js/electron.js’.
I had tried using the latest node too - I downgraded to v6.9.4 just on the off chance it was a versioning thing but as you can see no go.