You can allow the driver installation in your System Preferences, under Security and Privacy. Near the bottom of this window you will see a prompt letting you know that 'Some system software was blocked from loading'.
Click on the Allow button next to this.
Then select the items related to Squirrels and click OK. The drivers should now install normally on your Mac.
If you're not seeing the 'Some system software was blocked from loading' message in the Security & Privacy window, make sure you're doing the following.
Open Security & Privacy before rebooting the Mac