Error: Cannot find module 'cheerio' on OS X

I can't seem to do anything with Keybase any more. It was working fine for the last year or so, but has now died. I tried to do an update through the command line but it failed. I tried to install the new client (from the .dmg) but this fails before the login stage (just hangs).


```

module.js:328
throw err;
^

Error: Cannot find module 'cheerio'
at Function.Module._resolveFilename (module.js:326:15)
at Function.Module._load (module.js:277:25)
at Module.require (module.js:354:17)
at require (internal/module.js:12:17)
at Object. (/usr/local/lib/node_modules/keybase/lib/sigchain.js:32:13)
at Object. (/usr/local/lib/node_modules/keybase/lib/sigchain.js:923:4)
at Module._compile (module.js:398:26)
at Object.Module._extensions..js (module.js:405:10)
at Module.load (module.js:344:32)
at Function.Module._load (module.js:301:12)
```

Start with the stack trace in /usr/local/lib/node_modules/keybase/lib/sigchain.js, especially line 32, and reproduce the command-line update or .dmg installation on OS X. Done means the Keybase client installs or updates successfully without the missing 'cheerio' module error.

Written by the indexing model from the issue text.