Core issue
This problem occurs due to the presence of Cisco bug ID CSCsc23718.
The ERROR: Command requires failover license error message displays after an upgrade a PIX with a Restricted Feature License to 7.0.
The error is simply cosmetic and does not affect the operation of the device.
Resolution
In order to resolve this issue, download and upgrade the PIX software version to 7.0(3.4) or a later version.