I need to detect kLSMultipleInstancesProhibitedErr Apply/OS-X event inside my Python app

I need to detect kLSMultipleInstancesProhibitedErr Apply/OS-X event inside
my Python app

My python app which is single instance app and can not be launched two
instance at a time. I did it using LSMultipleInstancesProhibited:True
inside plist. I need to detect "kLSMultipleInstancesProhibitedErr"
Apple/OS-X event inside my Python program and need to show appropriate
message.
"kLSMultipleInstancesProhibitedErr" is triggered when user try to launch
second instance.