Replace relative imports by absolute imports because pytest

Author: Matthias Koeppe

src/sage/matrix/matrix_integer_dense_hnf.py

@@ -9,14 +9,13 @@
 from copy import copy
 
 from sage.arith.misc import CRT_list, previous_prime
+from sage.matrix.constructor import identity_matrix, matrix, random_matrix
 from sage.misc.misc import cputime
 from sage.misc.verbose import verbose
 from sage.rings.integer import Integer
 from sage.rings.integer_ring import ZZ
 from sage.rings.real_mpfr import RR
 
-from .constructor import identity_matrix, matrix, random_matrix
-
 
 def max_det_prime(n):
     """

src/sage/matrix/matrix_integer_dense_saturation.py

@@ -5,14 +5,13 @@
 from copy import copy
 
 from sage.arith.misc import binomial, GCD as gcd
+from sage.matrix import matrix_integer_dense_hnf
+from sage.matrix.constructor import identity_matrix, random_matrix
 from sage.misc.randstate import current_randstate
 from sage.misc.verbose import verbose
 from sage.rings.finite_rings.finite_field_constructor import FiniteField as GF
 from sage.rings.integer_ring import ZZ
 
-from . import matrix_integer_dense_hnf
-from .constructor import identity_matrix, random_matrix
-
 
 def p_saturation(A, p, proof=True):
     """