To reproduce:
1. Inport and set-up perforce
2. Sync a PSD texture from Perforce, but do not check it out
3. In the Project view duplicate an asset that is not already checked-out
4. Double click the texture in the Project view to open in Photoshop (you
may need to set Photoshop as your default image editor)
5. Make a change to the texture and press Ctrl-S to save the image.
6. You will receive an error that the file could not be saved. The error is a result of the file being read-only.