I missing Qupzilla.
Your script cannot find QupZilla

I have modify it in this way:

"
def find_browsers():
apps = [
'Chrome',
'Chromium',
'chromium-browser',
'firefox',
'Firefox',
'Google Chrome',
'google-chrome',
'opera',
'Opera',
'qupzilla',
'QupZilla',
'SeaMonkey',
'seamonkey',
]
"