Description of problem:
rhcert-backend certification can encounter a TypeError with traceback during execution of the 'plan' command.

Version-Release number of selected component (if applicable):
redhat-certification-1.0-20150325.el7

How reproducible:


Steps to Reproduce:
1. start `rhcert-backend plan`
2. state that the system is being used for certification
3. press <enter> for each of the following questions.

Actual results:
traceback on TypeError after 'What certification is this system being tested for?' when blank answer is given.

Also note that the prompt in question ends with '?' not '? ' (no trailing space).

Expected results:
rhcert-backend survives the error.  Prompting again whether this is for certification or similar would be helpful.

Additional info:
# rhcert-backend plan
Verifying test plan
Warning: default plan called
Hardware: LENOVO 4384BN5 4384BN5
OS: Maipo 7.1

Please verify the hardware product information:
    Vendor:
    Make:
    Model:
    Product URL:
    Specification URL:
    Support URL:
    category (Desktop/Workstation|Laptop|Component/Peripheral|Server) Server
response: Server

Is this system being tested for certification? (yes|no) yes
response: yes

response: True
Searching...
Red Hat Catalog User Name: 
Password: 
Searching...

done.
Could not find any matching certification
What certification is this system being tested for?Traceback (most recent call last):
  File "/usr/bin/rhcert-backend", line 37, in <module>
    success = rhcertBackend.do(args)
  File "/usr/lib/python2.7/site-packages/rhcert/client/backend.py", line 171, in do
    result = self.commands[self.command]()
  File "/usr/lib/python2.7/site-packages/rhcert/client/harness.py", line 184, in doPlan
    self.doDiscover()
  File "/usr/lib/python2.7/site-packages/rhcert/client/harness.py", line 110, in doDiscover
    self.editCertification()
  File "/usr/lib/python2.7/site-packages/rhcert/client/harness.py", line 1126, in editCertification
    self.catalog.getCertificationID(self.certification)
  File "/usr/lib/python2.7/site-packages/rhcert/catalog.py", line 276, in getCertificationID
    answer = self.ui.prompt("What certification is this system being tested for?", answers)
  File "/usr/lib/python2.7/site-packages/rhcert/testUI.py", line 53, in prompt
    return self.ui.prompt(message, validation, default)
  File "/usr/lib/python2.7/site-packages/rhcert/commandLineUI.py", line 51, in prompt
    error = validation(response.strip())
TypeError: 'list' object is not callable