I've added an exploit from www.exploit-db.com to /.msf4/modules/exploit/windows/remote/41987.py following the naming convention. I updated the database with the command updatedb and rebooted. 
Metasploit does not detect the newly added exploit. However, if i add 41891.rb, it detects it no problem.  Why does Metasploit not see the python files?
Because metasploit is purely written in Ruby.
Metasploit does't detect added exploit from exploit-db