PGAdmin 4 OSX app "…is damaged and can’t be opened"

Hello,

The version I downloaded is pgAdmin 4 v1.6 (released July 13, 2017) https://www.postgresql.org/ftp/pgadmin/pgadmin4/v1.6/macos/

It verified with the signature:

$ gpg2 --verify pgadmin4-1.6.dmg.sig pgadmin4-1.6.dmg
gpg: Signature made Tue 11 Jul 14:36:37 2017 BST using RSA key ID 698F1519
gpg: Good signature from "Dave Page <dpage(at)pgadmin(dot)org>" [unknown]
gpg: aka "Dave Page <pgsnake(at)gmail(dot)com>" [unknown]
gpg: aka "Dave Page <dpage(at)postgresql(dot)org>" [unknown]
gpg: aka "Dave Page <dave(dot)page(at)enterprisedb(dot)com>" [unknown]
gpg: WARNING: This key is not certified with a trusted signature!
gpg: There is no indication that the signature belongs to the owner.
Primary key fingerprint: E0C4 CEEB 826B 1FDA 4FB4 68E0 24AD FAAF 698F 1519

The error comes upon running the app, and after the “this app has been download… verify you want to open it” etc, a Finder pop up reads: "pgAdmin 4.app is damaged and can’t be opened” (attached screen shot).

The machine is running OSX 10.9.5, and has a working Postgres 9 install and PGAdmin 3.

Let me know if there’s any further info you need from me.

Regards,
iain