Use spawn instead of exec to execute command (Fixes #171)

[JeffreyCA]

Fixes #171

The following Python code now runs to completion without having to set runInTerminal to true.

for count in range(100000):
    print(count)

When using spawn, the stdout and stderr data object is a uint8array so it needs to be decoded into a string before appending to the output channel.

[formulahendry]

What's the difference between decoder.decode(data) and data.toString()? Others look good to me!

[JeffreyCA]

Calling toString() on data (a uint8array) results in a string representation of the int array, not the actual decoded value.

Also see this

[formulahendry]

Seems like the official doc also use data.toString() :https://nodejs.org/api/child_process.html#child_process_child_process_spawn_command_args_options
And I have tried data.toString(), the output is the same decoder.decode(data). Just want to know if there is any case needed to use decoder.decode(data), since data.toString() would be simple.

[JeffreyCA]

You're right, this was a couple of months ago so I don't remember exactly why I used TextDecoder. I have made the change.

[formulahendry]

Thanks @JeffreyCA !