Description of problem:
when executing the network diagnostics ansible check playbook, meet below error:
ValueError: time data 'Tue 2018-08-07 23:09:46 EDT' does not match format '%a %Y-%m-%d %H:%M:%S %Z'

Version-Release number of selected component (if applicable):
openshift-ansible-3.11.0-0.11.0.git.0.3c66516None.noarch.rpm

How reproducible:
always

Steps to Reproduce:
1. prepare the hosts file qe-inventory
2. ansible-playbook -i qe-inventory -l all,localhost ./openshift-ansible/playbooks/openshift-checks/adhoc.yml -e openshift_checks=sdn -e openshift_checks_output_dir=$HOME/tmp/aws/output


Actual results:
Failure summary:


  1. Hosts:    ec2-x-x-x-x.compute-1.amazonaws.com
     Play:     OpenShift Health Checks
     Task:     Run health checks (adhoc)
     Message:  One or more checks failed
     Details:  check "sdn":
               time data 'Tue 2018-08-07 23:09:46 EDT' does not match format '%a %Y-%m-%d %H:%M:%S %Z'
               Traceback (most recent call last):
                 File "/root/openshift-ansible/roles/openshift_health_checker/action_plugins/openshift_health_check.py", line 225, in run_check
                   result = check.run()
                 File "/root/openshift-ansible/roles/openshift_health_checker/openshift_checks/sdn.py", line 71, in run
                   self.check_node()
                 File "/root/openshift-ansible/roles/openshift_health_checker/openshift_checks/sdn.py", line 239, in check_node
                   self.save_service_logs('%s-node' % service_prefix)
                 File "/root/openshift-ansible/roles/openshift_health_checker/openshift_checks/sdn.py", line 341, in save_service_logs
                   '%a %Y-%m-%d %H:%M:%S %Z')
                 File "/usr/lib64/python2.7/_strptime.py", line 332, in _strptime
                   (data_string, format))
               ValueError: time data 'Tue 2018-08-07 23:09:46 EDT' does not match format '%a %Y-%m-%d %H:%M:%S %Z'


Expected results:
should not have the error

Additional info:
seems datetime.strptime() just can recognize timezone "UTC" "EST", but cannot understand "EDT".
for example: 
>>> start_timestamp = 'Tue 2018-08-07 23:09:38 UTC'
>>> since_date = datetime.datetime.strptime(start_timestamp, '%a %Y-%m-%d %H:%M:%S %Z')