Description of problem:
Sometimes virt-who failed to send host/guest mapping info to SAM as "Communication with subscription manager failed with code 500: undefined local variable or method `hypervisor' for #<Class:0x000000055ee1b0>"

Version-Release number of selected component (if applicable):
virt-who-0.16-7.el6.noarch
subscription-manager-1.16.8-5.el6.x86_64
python-rhsm-1.16.6-1.el6.x86_64

How reproducible:
20%

Steps to Reproduce:
1. Register system to SAM
2. Configure virt-who run at esx mode and restart virt-who,check virt-who's log.
[root@dell-per310-01 product]# cat /etc/sysconfig/virt-who  | grep -v ^# | grep -v ^$
VIRTWHO_DEBUG=1
VIRTWHO_ESX=1
VIRTWHO_ESX_OWNER=ACME_Corporation
VIRTWHO_ESX_ENV=Library
VIRTWHO_ESX_SERVER=10.66.79.5
VIRTWHO_ESX_USERNAME=administrator
VIRTWHO_ESX_PASSWORD=qwer1234P!
[root@dell-per310-01 product]# service virt-who restart && tail -f /var/log/rhsm/rhsm.log
[root@dell-per310-01 product]# service virt-who restart
Stopping virt-who:                                         [  OK  ]
Starting virt-who:                                         [  OK  ]
..................
hosts-to-guests mapping for config "env/cmdline": 2 hypervisors and 2 guests found
2016-03-17 01:48:39,614 [virtwho.main DEBUG] MainProcess(5675):MainThread @subscriptionmanager.py:hypervisorCheckIn:186 - Host-to-guest mapping: {
    "aee4ff00-8c33-11e2-994a-6c3be51d959a": [
        {
            "guestId": "42092ca4-1f26-bf00-b9c9-593e3b41abda", 
            "state": 5, 
            "attributes": {
                "active": 0, 
                "hypervisorVersion": "6.0.0", 
                "virtWhoType": "esx", 
                "hypervisorType": "VMware ESXi"
            }
        }, 
        {
            "guestId": "4209a518-e1de-ecf2-6625-faacc5b052c2", 
            "state": 5, 
            "attributes": {
                "active": 0, 
                "hypervisorVersion": "6.0.0", 
                "virtWhoType": "esx", 
                "hypervisorType": "VMware ESXi"
            }
        }
    ], 
    "86b2bd00-8bad-11e2-87f4-6c3be514699d": []
}
2016-03-17 01:48:40,505 [virtwho.main ERROR] MainProcess(5675):MainThread @virtwho.py:send:203 - Unable to send data: Communication with subscription manager failed with code 500: undefined local variable or method `hypervisor' for #<Class:0x0000000585dd60>

Actual results:
Virt-who can't send host/guest mapping info to SAM as "500 error" with subscription-manager

Expected results:
Virt-who can send host/guest mapping info to SAM, it shouldn't show any error info in the log.

Additional info: