Cleanup python 2.7 handling logic

We have several codes to handle the differences between py2 and py3.
py2 support has been dropped so there is no need for them now.

Change-Id: I30080f4e1a5ac04860c4341d966ee53131eb2022

horizon/base.py

@@ -52,15 +52,6 @@ from horizon.utils import settings as utils_settings
 DEFAULT_PANEL_GROUP = 'default'
 LOG = logging.getLogger(__name__)
 
-# Python 3.8 removes the ability to import the abstract base classes from
-# 'collections', but 'collections.abc' is not present in Python 2.7
-# TODO(stephenfin): Remove when we drop support for Python 2.7
-# pylint: disable=ungrouped-imports
-if hasattr(collections, 'abc'):
-    from collections.abc import Iterable
-else:
-    from collections import Iterable
-
 
 def _decorate_urlconf(urlpatterns, decorator, *args, **kwargs):
     for pattern in urlpatterns:
@@ -599,8 +590,8 @@ class Dashboard(Registry, HorizonComponent):
         default_created = False
         for panel_set in self.panels:
             # Instantiate PanelGroup classes.
-            if not isinstance(panel_set, Iterable) and \
-                    issubclass(panel_set, PanelGroup):
+            if (not isinstance(panel_set, collections.abc.Iterable) and
+                    issubclass(panel_set, PanelGroup)):
                 panel_group = panel_set(self)
             # Check for nested tuples, and convert them to PanelGroups
             elif not isinstance(panel_set, PanelGroup):

horizon/tables/base.py

@@ -47,30 +47,12 @@ from horizon.tables.actions import LinkAction
 from horizon.utils import html
 from horizon.utils import settings as utils_settings
 
-# Python 3.8 removes the ability to import the abstract base classes from
-# 'collections', but 'collections.abc' is not present in Python 2.7
-# TODO(stephenfin): Remove when we drop support for Python 2.7
-# pylint: disable=ungrouped-imports
-if hasattr(collections, 'abc'):
-    from collections.abc import Mapping
-else:
-    from collections import Mapping
-
 
 LOG = logging.getLogger(__name__)
 PALETTE = termcolors.PALETTES[termcolors.DEFAULT_PALETTE]
 STRING_SEPARATOR = "__"
 
 
-# 'getfullargspec' is Python 3-only, but 'getargspec' is deprecated for removal
-# in Python 3.6
-# TODO(stephenfin): Remove 'getargspec' when we drop support for Python 2.7
-if hasattr(inspect, 'getfullargspec'):
-    getargspec = inspect.getfullargspec
-else:
-    getargspec = inspect.getargspec
-
-
 class Column(html.HTMLElement):
     """A class which represents a single column in a :class:`.DataTable`.
 
@@ -413,7 +395,8 @@ class Column(html.HTMLElement):
         if callable(self.transform):
             data = self.transform(datum)
         # Dict lookups
-        elif isinstance(datum, Mapping) and self.transform in datum:
+        elif (isinstance(datum, collections.abc.Mapping) and
+              self.transform in datum):
             data = datum.get(self.transform)
         else:
             # Basic object lookups
@@ -485,7 +468,7 @@ class Column(html.HTMLElement):
                 return None
         obj_id = self.table.get_object_id(datum)
         if callable(self.link):
-            if 'request' in getargspec(self.link).args:
+            if 'request' in inspect.getfullargspec(self.link).args:
                 return self.link(datum, request=self.table.request)
             return self.link(datum)
         try:

horizon/test/helpers.py

@@ -44,15 +44,6 @@ from django.contrib.staticfiles.testing \
 
 from horizon import middleware
 
-# Python 3.8 removes the ability to import the abstract base classes from
-# 'collections', but 'collections.abc' is not present in Python 2.7
-# TODO(stephenfin): Remove when we drop support for Python 2.7
-# pylint: disable=ungrouped-imports
-if hasattr(collections, 'abc'):
-    from collections.abc import Mapping
-else:
-    from collections import Mapping
-
 
 LOG = logging.getLogger(__name__)
 
@@ -335,8 +326,8 @@ class update_settings(django_test_utils.override_settings):
         if keep_dict:
             for key, new_value in kwargs.items():
                 value = getattr(settings, key, None)
-                if (isinstance(new_value, Mapping) and
-                        isinstance(value, Mapping)):
+                if (isinstance(new_value, collections.abc.Mapping) and
+                        isinstance(value, collections.abc.Mapping)):
                     copied = copy.copy(value)
                     copied.update(new_value)
                     kwargs[key] = copied

openstack_dashboard/api/base.py

@@ -16,7 +16,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-from collections import abc as collections
+import collections.abc
 import functools
 
 from django.conf import settings
@@ -220,7 +220,7 @@ class Quota(object):
         return "<Quota: (%s, %s)>" % (self.name, self.limit)
 
 
-class QuotaSet(collections.Sequence):
+class QuotaSet(collections.abc.Sequence):
     """Wrapper for client QuotaSet objects.
 
     This turns the individual quotas into Quota objects

openstack_dashboard/test/integration_tests/decorators.py

@@ -18,15 +18,6 @@ import testtools
 
 from openstack_dashboard.test.integration_tests import config
 
-# Python 3.8 removes the ability to import the abstract base classes from
-# 'collections', but 'collections.abc' is not present in Python 2.7
-# TODO(stephenfin): Remove when we drop support for Python 2.7
-# pylint: disable=ungrouped-imports
-if hasattr(collections, 'abc'):
-    from collections.abc import Iterable
-else:
-    from collections import Iterable
-
 
 def _is_test_method_name(method):
     return method.startswith('test_')
@@ -165,7 +156,7 @@ def skip_because(**kwargs):
     def actual_decoration(obj):
         skip_method = _get_skip_method(obj)
         bugs = kwargs.get("bugs")
-        if bugs and isinstance(bugs, Iterable):
+        if bugs and isinstance(bugs, collections.abc.Iterable):
             for bug in bugs:
                 if not bug.isdigit():
                     raise ValueError("bug must be a valid bug number")