SyntaxError: Block-scoped declarations - npm start

Hi I have a fresh install and on running npm start I’m getting an error

SyntaxError: Block-scoped declarations

I’ve attached my npm-debug.log

0 info it worked if it ends with ok
1 verbose cli [ '/Users/chrisknight/.nodenv/versions/v4.4.7/bin/node',
1 verbose cli   '/Users/chrisknight/.nodenv/versions/v4.4.7/bin/npm',
1 verbose cli   'start' ]
2 info using npm@2.15.8
3 info using node@v4.4.7
4 verbose run-script [ 'prestart', 'start', 'poststart' ]
5 info prestart sage@9.0.0-alpha.3
6 info start sage@9.0.0-alpha.3
7 verbose unsafe-perm in lifecycle true
8 info sage@9.0.0-alpha.3 Failed to exec start script
9 verbose stack Error: sage@9.0.0-alpha.3 start: `npm run build -s -- --watch`
9 verbose stack Exit status 1
9 verbose stack     at EventEmitter.<anonymous> (/Users/chrisknight/.nodenv/versions/v4.4.7/lib/node_modules/npm/lib/utils/lifecycle.js:217:16)
9 verbose stack     at emitTwo (events.js:87:13)
9 verbose stack     at EventEmitter.emit (events.js:172:7)
9 verbose stack     at ChildProcess.<anonymous> (/Users/chrisknight/.nodenv/versions/v4.4.7/lib/node_modules/npm/lib/utils/spawn.js:24:14)
9 verbose stack     at emitTwo (events.js:87:13)
9 verbose stack     at ChildProcess.emit (events.js:172:7)
9 verbose stack     at maybeClose (internal/child_process.js:827:16)
9 verbose stack     at Process.ChildProcess._handle.onexit (internal/child_process.js:211:5)
10 verbose pkgid sage@9.0.0-alpha.3
11 verbose cwd /Users/chrisknight/Sites/today/site/web/app/themes/sage
12 error Darwin 14.5.0
13 error argv "/Users/chrisknight/.nodenv/versions/v4.4.7/bin/node" "/Users/chrisknight/.nodenv/versions/v4.4.7/bin/npm" "start"
14 error node v4.4.7
15 error npm  v2.15.8
16 error code ELIFECYCLE
17 error sage@9.0.0-alpha.3 start: `npm run build -s -- --watch`
17 error Exit status 1
18 error Failed at the sage@9.0.0-alpha.3 start script 'npm run build -s -- --watch'.
18 error This is most likely a problem with the sage package,
18 error not with npm itself.
18 error Tell the author that this fails on your system:
18 error     npm run build -s -- --watch
18 error You can get information on how to open an issue for this project with:
18 error     npm bugs sage
18 error Or if that isn't available, you can get their info via:
18 error
18 error     npm owner ls sage
18 error There is likely additional logging output above.
19 verbose exit [ 1, true ]

Is this an issue with sage - I’ve not seen it before, or my npm setup?

I just ran into something similar. For the moment, try locking webpack to beta 22: "webpack": "2.1.0-beta.22", in package.json, remove the ^

I found that updating my node to the current v6.7.0 fixed the problem without the need to lock down the webpack version,