fix: is_rockpi and is_raspberry_pi should not break outside Balena

[marvinmarnold]

User Story
As a user, I should not hit an exception if running outside Balena.

Notes
We currently detect hardware by inspecting the BALENA_DEVICE_TYPE environment variable, created by Balena. In test cases, this will raise an exception.

    def is_raspberry_pi():
        """
        Pulled from
        https://www.balena.io/docs/reference/base-images/devicetypes/
        """
        device_type = os.getenv('BALENA_DEVICE_TYPE')
        device_type_match = [
            'raspberry-pi2',
            'raspberrypi3',
            'raspberrypi3-64',
            'raspberrypi4-64',
            'nebra-hnt',
            'raspberrypicm4-ioboard'
        ]
    
        for device in device_type_match:
>           if device in device_type:
E           TypeError: argument of type 'NoneType' is not iterable

Acceptance Criteria

• is_rockpi and is_raspberry_pi should not raise exceptions if invoked outside Balena. Return False in both cases.

[shawaj]

@marvinmarnold for the version check, perhaps we could use cat /proc/device-tree/model when not on balena...

This gives the following output:

ROCK PI 4B
Raspberry Pi Compute Module 3 Plus Rev 1.0

[shawaj]

/proc/cpuinfo has this for RasPi too but not RockPi

[vpetersson]

@marvinmarnold for the version check, perhaps we could use cat /proc/device-tree/model when not on balena...

This gives the following output:

ROCK PI 4B Raspberry Pi Compute Module 3 Plus Rev 1.0

Seems like a reasonable fallback.

[shawaj]

Partially solved by #84