Description of problem:
While executing "ceph-medic --inventory /path/to/host check" command with invalid inventory path, returned error which was not user friendly.


Version-Release number of selected component (if applicable):
ceph-medic 1.0.2

How reproducible:
Always

Steps to Reproduce:
1. Try to check health of a ceph cluster  using ceph-medic.


Actual results:

Traceback (most recent call last):
  File "/usr/bin/ceph-medic", line 6, in <module>
    main.Medic()
  File "/usr/lib/python2.7/dist-packages/ceph_medic/main.py", line 44, in __init__
    self.main(argv)
  File "/usr/lib/python2.7/dist-packages/ceph_medic/decorators.py", line 45, in newfunc
    return f(*a, **kw)
  File "/usr/lib/python2.7/dist-packages/ceph_medic/main.py", line 120, in main
    ceph_medic.config.get('--inventory', self.hosts_file)))
  File "/usr/lib/python2.7/dist-packages/ceph_medic/util/configuration.py", line 106, in load_hosts
    return AnsibleInventoryParser(_path)
  File "/usr/lib/python2.7/dist-packages/ceph_medic/util/configuration.py", line 280, in __init__
    with open(filename, 'r') as fh:
IOError: [Errno 2] No such file or directory: '/etc/ansible/hostss'

Expected results:
Invalid path