won't build... problem with node package

[strohrdanz]

0 info it worked if it ends with ok
1 verbose cli [ 'node', '/usr/local/bin/npm', 'run', 'watch' ]
2 info using [email protected]
3 info using [email protected]
4 verbose run-script [ 'prewatch', 'watch', 'postwatch' ]
5 info prewatch [email protected]
6 info watch [email protected]
7 verbose unsafe-perm in lifecycle true
8 info [email protected] Failed to exec watch script
9 verbose stack Error: [email protected] watch: `webpack -w`
9 verbose stack spawn ENOENT
9 verbose stack     at ChildProcess.<anonymous> (/usr/local/lib/node_modules/npm/lib/utils/spawn.js:17:16)
9 verbose stack     at ChildProcess.emit (events.js:110:17)
9 verbose stack     at maybeClose (child_process.js:1015:16)
9 verbose stack     at Process.ChildProcess._handle.onexit (child_process.js:1087:5)
10 verbose pkgid [email protected]
11 verbose cwd /Applications/mamp/htdocs/webgl
12 error Darwin 14.5.0
13 error argv "node" "/usr/local/bin/npm" "run" "watch"
14 error node v0.12.7
15 error npm  v2.11.3
16 error file sh
17 error code ELIFECYCLE
18 error errno ENOENT
19 error syscall spawn
20 error [email protected] watch: `webpack -w`
20 error spawn ENOENT
21 error Failed at the [email protected] watch script 'webpack -w'.
21 error This is most likely a problem with the codrops-photoeffect-test package,
21 error not with npm itself.
21 error Tell the author that this fails on your system:
21 error     webpack -w
21 error You can get their info via:
21 error     npm owner ls codrops-photoeffect-test
21 error There is likely additional logging output above.
22 verbose exit [ 1, true ]