What is the Python package "wheel" and should it be a dependency?

[tanius]

During installation on Ubuntu 16.04 LTS, I needed to do

pip install wheel

before I could successfully do

pip install -r requirements.txt

The symptoms of the problem are shown here, and the solutions proposed there are confusing. It is not yet clear to me if wheel should be a dependency that goes into requirements.txt or if it's something missing in the system's Python environment.

To be found out, and fixed accordingly.