Typo in error message "perfrom" instead of "perform":
Connected to MyCluster1 at x.x.x.x:9160.
[cqlsh 4.0.1 | Cassandra 2.0.1 | CQL spec 3.0.0 | Thrift protocol 19.37.0]
Use HELP for help.
cqlsh> create user hari with password 'mypass';
Bad Request: Only superusers are allowed to perfrom CREATE USER queries