message: ENH: improve error message in Plane constructor.
diff: @@ -326,8 +326,7 @@ Plane< T, NDIMS >::Plane( const T* x1, const T* x2, const T* x3 )
  }
  SLIC_ERROR_IF( degenerate,
  - "cannot construct plane from supplied points." <<
  - "Supplied points form a degenerate line(in 2D) or triangle(in 3D)" );
  + "Supplied points form a degenerate " << (NDIMS==2) ? "line" : "triangle");
  numerics::normalize( m_normal, NDIMS );
  m_offset = numerics::dot_product( m_normal, x1, NDIMS );
  