Description of problem:
I refer to bug 632199#c13

Version-Release number of selected component (if applicable):
qa-tools-2.0-18

How reproducible:
always

Steps to Reproduce:
1. bkr workflow-tcms --errata 2010:10352 --new --task=/CoreOS/mysql/Security/CVE-2010-3839-JOIN-hang-in-stored-proc

 
Actual results:
Traceback (most recent call last):
  File "/usr/bin/bkr", line 9, in <module>
    load_entry_point('bkr.client==0.5.63', 'console_scripts', 'bkr')()
  File "/usr/lib/python2.7/site-packages/bkr/client/main.py", line 55, in main
    return parser.run()
  File "/usr/lib/python2.7/site-packages/kobo/cli.py", line 282, in run
    cmd.run(*cmd_args, **cmd_kwargs)
  File
"/usr/lib/python2.7/site-packages/bkr/client/commands/cmd_workflow_tcms.py",
line 491, in run
    job.schedule([TestRun(id) for id in runs])
  File
"/usr/lib/python2.7/site-packages/bkr/client/commands/cmd_workflow_tcms.py",
line 415, in schedule
    self.check_environment()
  File
"/usr/lib/python2.7/site-packages/bkr/client/commands/cmd_workflow_tcms.py",
line 244, in check_environment
    self.distro = self.runs[0].build
IndexError: list index out of range


Expected results:
pretty error message

Additional info:
if bug 673108 is resolved, this is in vain, as this wouldn't be error condition - however, a bit more care about the (unexpected) inputs is always nice ...