presto-plugin-toolkit/src/main/java/io/prestosql/plugin/base/authentication/KerberosAuthentication.java/KerberosAuthentication/KerberosAuthentication
class KerberosAuthentication:    public KerberosAuthentication(String principal, String keytabLocation)
    {
        requireNonNull(principal, "principal is null");
        requireNonNull(keytabLocation, "keytabLocation is null");
        Path keytabPath = Paths.get(keytabLocation);
        checkArgument(exists(keytabPath), "keytab does not exist: " + keytabLocation);
        checkArgument(isReadable(keytabPath), "keytab is not readable: " + keytabLocation);
        this.principal = createKerberosPrincipal(principal);
        this.configuration = createConfiguration(this.principal.getName(), keytabLocation);
    }