message: Rename Eigen3 as Eigen (sphinx warning)
diff: @@ -138,7 +138,7 @@ Documentation
  To build the documentation, `sphinx-doc <http://www.sphinx-doc.org>`_ and
  `sphinxcontrib-bibtex <https://sphinxcontrib-bibtex.readthedocs.io>`_ are
  -required. As the documentation is auto-tested, `CGAL`_, `Eigen3`_,
  +required. As the documentation is auto-tested, `CGAL`_, `Eigen`_,
  `Matplotlib`_, `NumPy`_ and `SciPy`_ are also mandatory to build the
  documentation.
  