trac #17096 fixing two doctests

Author: Frédéric Chapoton

src/sage/combinat/ncsf_qsym/generic_basis_code.py

@@ -940,15 +940,16 @@ def degree(self):
                 sage: S.zero().degree()
                 Traceback (most recent call last):
                 ...
-                ValueError: The zero element does not have a well-defined degree.
+                ValueError: the zero element does not have a well-defined degree
                 sage: F = QuasiSymmetricFunctions(QQ).F()
                 sage: F.zero().degree()
                 Traceback (most recent call last):
                 ...
-                ValueError: The zero element does not have a well-defined degree.
+                ValueError: the zero element does not have a well-defined degree
             """
             return self.maximal_degree()
 
+
 class AlgebraMorphism(ModuleMorphismByLinearity): # Find a better name
     """
     A class for algebra morphism defined on a free algebra from the image of the generators