Cannot install chromosomer
Chromosomer only exists for Python 2. You should thus be able to install it via

pip2 install chromosomer




But:

Your Python installation is a bit screwed up: there are Python 2 and Python 3, which are unfortunately incompatible.

On your system python and pip seem to be aliases for Python 3, which I’d strongly recommend against (lots of tools will break). Instead, they should alias Python 2. Python 3 should be invoked via python3/pip3.