]$ nova
Traceback (most recent call last):
  File "/usr/bin/nova", line 9, in <module>
    load_entry_point('python-novaclient==2.10.0', 'console_scripts', 'nova')()
  File "/usr/lib/python2.7/site-packages/pkg_resources.py", line 337, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File "/usr/lib/python2.7/site-packages/pkg_resources.py", line 2311, in load_entry_point
    return ep.load()
  File "/usr/lib/python2.7/site-packages/pkg_resources.py", line 2017, in load
    entry = __import__(self.module_name, globals(),globals(), ['__name__'])
  File "/usr/lib/python2.7/site-packages/novaclient/shell.py", line 37, in <module>
    from novaclient.v1_1 import shell as shell_v1_1
  File "/usr/lib/python2.7/site-packages/novaclient/v1_1/shell.py", line 27, in <module>
    from novaclient.openstack.common import timeutils
  File "/usr/lib/python2.7/site-packages/novaclient/openstack/common/timeutils.py", line 25, in <module>
    import iso8601
ImportError: No module named iso8601

# yum install python-iso8601 -y

$ nova
# works!