Error out rather than call python on the perl script
## This file is part of Mbed TLS (https://tls.mbed.org)
my $py = $0;
-$py =~ s/\.pl$/.py/;
+$py =~ s/\.pl$/.py/ or die "Unable to determine the name of the Python script";
exec 'python3', $py, @ARGV;
print STDERR "$0: python3: $!\n";
exec 'python', $py, @ARGV;
