Little code improvements

[Lampe2020]

→ Changed loop in createFd() to generator expression
→ Replace str.format() calls with f-strings
→ Replace double quotes with single quotes
→ Change printed messages so all of them contain an indicator if they are good ([+] ) or bad ([-] ) or neutral ( )
→ Change shebang to be more universal (#!/usr/bin/python3 → #!/usr/bin/env python3)