Fix namedtuples and reactivate tests for Python 2

jedi/plugins/stdlib.py

@@ -32,7 +32,8 @@ from jedi.evaluate.syntax_tree import is_string
 
 # Copied from Python 3.6's stdlib.
 _NAMEDTUPLE_CLASS_TEMPLATE = """\
-from builtins import property as _property, tuple as _tuple
+_property = property
+_tuple = tuple
 from operator import itemgetter as _itemgetter
 from collections import OrderedDict
 

test/test_evaluate/test_stdlib.py

@@ -7,14 +7,6 @@ from textwrap import dedent
 import pytest
 
 
-# The namedtuple is different for different Python2.7 versions. Some versions
-# are missing the attribute `_class_template`.
-@pytest.fixture(autouse=True)
-def skipping(environment):
-    if environment.version_info.major < 3:
-        pytest.skip()
-
-
 @pytest.mark.parametrize(['letter', 'expected'], [
     ('n', ['name']),
     ('s', ['smart']),