Description of problem:
When set a wrong service-level, the output is not friendly.

Version-Release number of selected component (if applicable):
subscription-manager-1.1.5-1.el6.x86_64
python-rhsm-1.1.4-1.el6.x86_64

How reproducible:
always

Steps to Reproduce:
1.register the system against the stage candlepin
2.set a wrong service-level with cmd:
#subscription-manager service-level --set=aaa

  
Actual results:
The output is:
Service level {0} is not available to consumers of organization 6752574

Expected results:
The output should be:
Service level aaa is not available to consumers of organization 6752574

Additional info: