I get the same error, need to update the firmware.
I have just ran curl -sS ... to up adept the firmware and get an error message line 697 cd: /home/pi/Pimoroni/flotilla/source/firmware no such file or directory.
I also added sudo in front of the command, same problem.
Under Pimoroni/flotilla there are two folders flotilla-offline and flotilla-rockpool .
No source file folder.
I am running on a B3, Jessie , ephinany browser, I have ran sudo apt-get update etc.
Confused
Steve