Anyone else using Manjaro may find that trying to use either a gui tool or yaourt from the cli it sems impossible to install python-pymediainfo.
I discovered that downloading from here then installing as a locall package was the only way I could achieve this.
The other dependencis were satisfied by yaourt using the 0.99. bzr release of rapid-photo-downloader from aur.
Very happy I can now run my goto software (without rebooting into my old Ubuntu environment). 
I guess my chain of poss have been less about this software and more about the quirks of getting it installed on this particular linux distro .