Crash when using with Sourcetree DIFF in 3.20: Cannot import gi / Cannot import GTK+: The specific module could not be found

Hi I get the following error when using source tree external DIFF.

Path : C:\Program Files (x86)\Meld\Meld.exe Arguments : $LOCAL $REMOTE

Error:

I'm assuming I am missing a something related to GTK? not sure what that is.

Thanks in advance

Reza