Failed to install hotfix 12, 13 on slave servers, error: the update precheck failed with an unknown error

When tried applying the hotfixes through the command line, the following error appears : 

The update precheck stage failed with an unknown error. 
update: XS71ECU1012
info: Retrieving key from file:///etc/pki/rpm-gpg/. 
http://10.x.x.x/update/exxxx/vdi/repodata/repomd.xml: [Errno -1] Gpg Keys not imported, cannot verify repomd.xml for repo XS71ECU1012
Trying other mirrors.

1. Edit the file : vi /etc/xapi.d/extensions/pool_update.precheck and press i to enter into insert mode

2. In the file ,look for def execute_precheck and enter '--nogpgcheck' separated by a comma in cmd section.
   Example : cmd = ['yum', 'install', '-y', '--noplugins', '--nogpgcheck', '-c', yum_conf_file, control_package]

3. Press escape to exit insert mode and save and quit the file by typing :wq

4. You can now apply hotfix 12,13 and 14 on the server.

Problem Cause