subprocess: don't use shell

[dotlambda]

There is no need to.

[xnetcat]

spotDL will crash if ffmpeg is not found, because Popen throws an exception FileNotFoundError: [WinError 2] The system cannot find the file specified before we check return code

this should work

    try:
        process = subprocess.Popen(
            ['ffmpeg', '-version'],
            stdout=subprocess.PIPE, stderr=subprocess.PIPE
        )
    except FileNotFoundError:
        print("FFmpeg was not found, spotDL cannot continue.", file=sys.stderr)
        return False

[Silverarmor]

Please pull changes from upstream/dev

[dotlambda]

@Silverarmor done