fix doctests

src/sage/geometry/polyhedron/ppl_lattice_polytope.py

@@ -855,8 +855,8 @@ def base_projection_matrix(self, fiber):
             sage: poly = LatticePolytope_PPL((-9,-6,-1,-1),(0,0,0,1),(0,0,1,0),(0,1,0,0),(1,0,0,0))
             sage: fiber = next(poly.fibration_generator(2))
             sage: poly.base_projection_matrix(fiber)
-            [0 0 1 0]
-            [0 0 0 1]
+            [ 0  0 -1  0]
+            [ 0  0  0 -1]
 
         Note that the basis choice in :meth:`base_projection` for the
         quotient is usually different::
@@ -866,7 +866,7 @@ def base_projection_matrix(self, fiber):
             sage: [ proj(p) for p in poly.integral_points() ]
             [(-1, -1), (0, 0), (0, 0), (0, 0), (0, 0), (0, 0), (0, 0), (0, 0), (0, 1), (1, 0)]
             sage: [ proj_matrix*p for p in poly.integral_points() ]
-            [(-1, -1), (0, 0), (0, 0), (0, 0), (0, 0), (0, 0), (0, 0), (0, 0), (0, 1), (1, 0)]
+            [(1, 1), (0, 0), (0, 0), (0, 0), (0, 0), (0, 0), (0, 0), (0, 0), (0, -1), (-1, 0)]
         """
         return matrix(ZZ, fiber.vertices()).right_kernel_matrix()
 

src/sage/matrix/matrix2.pyx

@@ -4405,10 +4405,6 @@ cdef class Matrix(Matrix1):
             Traceback (most recent call last):
             ...
             ValueError: 'pari' matrix kernel algorithm only available over non-trivial number fields and the integers, not over Rational Field
-            sage: matrix(Integers(6), 2, 2).right_kernel_matrix(algorithm='generic')
-            Traceback (most recent call last):
-            ...
-            NotImplementedError: Echelon form not implemented over 'Ring of integers modulo 6'.
             sage: matrix(QQ, 2, 2).right_kernel_matrix(algorithm='pluq')
             Traceback (most recent call last):
             ...