Remove logic for python 2 support

... because python 2 support was already removed.

Change-Id: I57e8ac2549ecf170d6b43bc0557fd388e025e536

oslo_reports/models/base.py

@@ -21,13 +21,9 @@ store unserialized data generated by generators during
 the report serialization process.
 """
 
+from collections import abc
 import copy
 
-try:  # python 3
-    from collections import abc
-except ImportError:  # python 2
-    import collections as abc
-
 
 class ReportModel(abc.MutableMapping):
     """A Report Data Model

oslo_reports/tests/test_base_report.py

@@ -12,13 +12,9 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+from collections import abc
 import re
 
-try:  # python 3
-    from collections import abc
-except ImportError:  # python 2
-    import collections as abc
-
 from oslotest import base
 
 from oslo_reports.models import base as base_model

oslo_reports/views/text/generic.py

@@ -18,10 +18,7 @@ This modules provides several generic views for
 serializing models into human-readable text.
 """
 
-try:  # python 3
-    from collections import abc
-except ImportError:  # python 2
-    import collections as abc
+from collections import abc
 
 
 class MultiView(object):

oslo_reports/views/xml/generic.py

@@ -23,14 +23,10 @@ and non-naive serializers check for this attribute and handle
 such strings specially)
 """
 
+from collections import abc
 import copy
 import xml.etree.ElementTree as ET
 
-try:  # python 3
-    from collections import abc
-except ImportError:  # python 2
-    import collections as abc
-
 from oslo_reports import _utils as utils