ModuleNotFoundError for packages that you don't want to install

[cmower]

I am setting up ver2 for ros-pybullet inteface, and I haven't installed TracIK on nextage pc - and probably won't at all since there is no need (we will use Exotica). However, an error is thrown when ik_ros is imported since it tried to import TracIK. Instead, this exception should be caught and a warning thrown to let user know that this particular IK interface is not available.