Unable to run shell command

[drakhart]

Hi! I'm using your MM module and loving it so far, thanks for your work!

Unfortunately I recently run into issues with it. All of a sudden I realized it was no longer turning on and off my monitor, and found this related error in the logs:

0|magicmir | [2021-09-26 15:54:09.290] [ERROR]  Whoops! There was an uncaught exception...
0|magicmir | [2021-09-26 15:54:09.294] [ERROR]  TypeError: exec is not a function
0|magicmir |     at Class.turnDisplayOff (/home/pi/MagicMirror/modules/mmm-toggle-by-mqtt/node_helper.js:85:9)
0|magicmir |     at MqttClient.<anonymous> (/home/pi/MagicMirror/modules/mmm-toggle-by-mqtt/node_helper.js:63:26)
0|magicmir |     at MqttClient.emit (events.js:200:13)
0|magicmir |     at MqttClient._handlePublish (/home/pi/MagicMirror/modules/mmm-toggle-by-mqtt/node_modules/mqtt/lib/client.js:1162:12)
0|magicmir |     at MqttClient._handlePacket (/home/pi/MagicMirror/modules/mmm-toggle-by-mqtt/node_modules/mqtt/lib/client.js:351:12)
0|magicmir |     at work (/home/pi/MagicMirror/modules/mmm-toggle-by-mqtt/node_modules/mqtt/lib/client.js:283:12)
0|magicmir |     at Writable.writable._write (/home/pi/MagicMirror/modules/mmm-toggle-by-mqtt/node_modules/mqtt/lib/client.js:294:5)
0|magicmir |     at doWrite (/home/pi/MagicMirror/modules/mmm-toggle-by-mqtt/node_modules/readable-stream/lib/_stream_writable.js:428:64)
0|magicmir |     at writeOrBuffer (/home/pi/MagicMirror/modules/mmm-toggle-by-mqtt/node_modules/readable-stream/lib/_stream_writable.js:417:5)
0|magicmir |     at Writable.write (/home/pi/MagicMirror/modules/mmm-toggle-by-mqtt/node_modules/readable-stream/lib/_stream_writable.js:334:11)
0|magicmir | [2021-09-26 15:54:09.307] [ERROR]  MagicMirror will not quit, but it might be a good idea to check why this happened. Maybe no internet connection?
0|magicmir | [2021-09-26 15:54:09.310] [ERROR]  If you think this really is an issue, please open an issue on GitHub: https://github.com/MichMich/MagicMirror/issues

I don't know why it started happening, because I didn't update or change either the tmp folder permissions, MM, Node, ShellJS or your module, but I found a related ShellJS issue where they're still trying to find an explanation: shelljs/shelljs#1024

Anyway I managed to fix it by getting rid of ShellJS in favor of Node's native child_process, so I'll be opening a PR soon... I guess there's no need to specify all the versions or how to reproduce the error (I wouldn't know how anyway).