pm2:prepare triggers warnings

[mryellow]

It doesn't seem to break anything, unsure when/where it popped up.

I'm running pm2 4.5.0 as a global install.

DEBUG=pm2:* NODE_OPTIONS="--trace-warnings" npm test

pm2:client Calling daemon method pm2:prepare on rpc socket:/home/user/.pm2/rpc.sock +27ms
(node:15665) Warning: Accessing non-existent property 'cat' of module exports inside circular dependency
    at emitCircularRequireWarning (internal/modules/cjs/loader.js:667:11)
    at Object.get (internal/modules/cjs/loader.js:681:5)
    at Object._register [as register] (/home/user/src/mfdc/agents/node_modules/shelljs/src/common.js:453:12)
    at Object.<anonymous> (/home/user/src/mfdc/agents/node_modules/shelljs/src/cat.js:4:8)
    at Module._compile (internal/modules/cjs/loader.js:1075:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1096:10)
    at Module.load (internal/modules/cjs/loader.js:940:32)
    at Function.Module._load (internal/modules/cjs/loader.js:781:14)
    at Module.require (internal/modules/cjs/loader.js:964:19)
    at require (internal/modules/cjs/helpers.js:88:18)
    at /home/user/src/mfdc/agents/node_modules/shelljs/shell.js:25:3
    at Array.forEach (<anonymous>)
    at Object.<anonymous> (/home/user/src/mfdc/agents/node_modules/shelljs/shell.js:24:23)
    at Module._compile (internal/modules/cjs/loader.js:1075:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1096:10)
    at Module.load (internal/modules/cjs/loader.js:940:32)
    at Function.Module._load (internal/modules/cjs/loader.js:781:14)
    at Module.require (internal/modules/cjs/loader.js:964:19)
    at require (internal/modules/cjs/helpers.js:88:18)
    at Object.Common.sink.resolveInterpreter (/home/user/src/mfdc/agents/node_modules/pm2/lib/Common.js:426:7)
    at Object.Common.prepareAppConf (/home/user/src/mfdc/agents/node_modules/pm2/lib/Common.js:198:17)
    at Object.Common.resolveAppAttributes (/home/user/src/mfdc/agents/node_modules/pm2/lib/Common.js:605:20)
    at /home/user/src/mfdc/agents/node_modules/pm2/lib/API.js:879:35
    at /home/user/src/mfdc/agents/node_modules/pm2-axon-rpc/lib/client.js:45:10
    at Parser.<anonymous> (/home/user/src/mfdc/agents/node_modules/pm2-axon/lib/sockets/req.js:67:8)
    at Parser.emit (events.js:314:20)
    at Parser._write (/home/user/src/mfdc/agents/node_modules/amp/lib/stream.js:91:16)
    at writeOrBuffer (_stream_writable.js:352:12)
    at Parser.Writable.write (_stream_writable.js:303:10)
    at Socket.ondata (_stream_readable.js:713:22)
    at Socket.emit (events.js:314:20)
    at addChunk (_stream_readable.js:303:12)
    at readableAddChunk (_stream_readable.js:279:9)
    at Socket.Readable.push (_stream_readable.js:218:10)
    at Pipe.onStreamRead (internal/stream_base_commons.js:188:23)