Replace relative imports by absolute imports because pytest

Author: Matthias Koeppe

src/sage/coding/linear_code.py

@@ -211,6 +211,9 @@ class should inherit from this class. Also ``AbstractLinearCode`` should never
 from sage.arith.misc import binomial, GCD
 from sage.categories.cartesian_product import cartesian_product
 from sage.categories.fields import Fields
+from sage.coding.decoder import Decoder
+from sage.coding.encoder import Encoder
+from sage.coding.linear_code_no_metric import AbstractLinearCodeNoMetric
 from sage.combinat.subset import Subsets
 from sage.cpython.string import bytes_to_str
 from sage.features.gap import GapPackage
@@ -230,10 +233,6 @@ class should inherit from this class. Also ``AbstractLinearCode`` should never
 from sage.rings.polynomial.polynomial_ring_constructor import PolynomialRing
 from sage.rings.rational_field import QQ
 
-from .encoder import Encoder
-from .decoder import Decoder
-from .linear_code_no_metric import AbstractLinearCodeNoMetric
-
 # *****************************************************************************
 # coding theory functions
 # *****************************************************************************