Sosreport fails with "ImportError: No module named concurrent.futures" error.

Issue

• Command sosreport fails with ImportError: No module named concurrent.futures error.

  /sbin/sosreport
  Traceback (most recent call last):
    File "/sbin/sosreport", line 14, in <module>
      from sos.sosreport import main
   File "/usr/lib/python2.7/site-packages/sos/sosreport.py", line 31, in <module>
      from concurrent.futures import ThreadPoolExecutor, TimeoutError
  ImportError: No module named concurrent.futures