docs: update stale Python 2 comments and docstrings

Author: mykaul

cassandra/datastax/graph/graphson.py

@@ -48,26 +48,26 @@
 ------------ | -------------- | -------------- | ------------
 text         | string         | string         | str
 boolean      |                |                | bool
-bigint       | g:Int64        | g:Int64        | long
+bigint       | g:Int64        | g:Int64        | int
 int          | g:Int32        | g:Int32        | int
 double       | g:Double       | g:Double       | float
 float        | g:Float        | g:Float        | float
 uuid         | g:UUID         | g:UUID         | UUID
 bigdecimal   | gx:BigDecimal  | gx:BigDecimal  | Decimal
 duration     | gx:Duration    | N/A            | timedelta              (Classic graph only)
 DSE Duration | N/A            | dse:Duration   | Duration               (Core graph only)
-inet         | gx:InetAddress | gx:InetAddress | str (unicode), IPV4Address/IPV6Address (PY3)
+inet         | gx:InetAddress | gx:InetAddress | str, IPV4Address/IPV6Address
 timestamp    | gx:Instant     | gx:Instant     | datetime.datetime
 date         | gx:LocalDate   | gx:LocalDate   | datetime.date
 time         | gx:LocalTime   | gx:LocalTime   | datetime.time
 smallint     | gx:Int16       | gx:Int16       | int
-varint       | gx:BigInteger  | gx:BigInteger  | long
+varint       | gx:BigInteger  | gx:BigInteger  | int
 date         | gx:LocalDate   | gx:LocalDate   | Date
 polygon      | dse:Polygon    | dse:Polygon    | Polygon
 point        | dse:Point      | dse:Point      | Point
 linestring   | dse:Linestring | dse:LineString | LineString
-blob         | dse:Blob       | dse:Blob       | bytearray, buffer (PY2), memoryview (PY3), bytes (PY3)
-blob         | gx:ByteBuffer  | gx:ByteBuffer  | bytearray, buffer (PY2), memoryview (PY3), bytes (PY3)
+blob         | dse:Blob       | dse:Blob       | bytearray, memoryview, bytes
+blob         | gx:ByteBuffer  | gx:ByteBuffer  | bytearray, memoryview, bytes
 list         | N/A            | g:List         | list                   (Core graph only)
 map          | N/A            | g:Map          | dict                   (Core graph only)
 set          | N/A            | g:Set          | set or list            (Core graph only)
@@ -969,7 +969,7 @@ def serialize(self, value, writer=None):
         """
         serializer = self.get_serializer(value)
         if not serializer:
-            raise ValueError("Unable to find a serializer for value of type: ".format(type(value)))
+            raise ValueError("Unable to find a serializer for value of type: {}".format(type(value)))
 
         val = serializer.serialize(value, writer or self)
         if serializer is TypeWrapperTypeIO:

cassandra/io/asyncorereactor.py

@@ -263,9 +263,9 @@ def _maybe_log_debug(self, *args, **kwargs):
         try:
             log.debug(*args, **kwargs)
         except Exception:
-            # TODO: Remove when Python 2 support is removed
-            # PYTHON-1266. If our logger has disappeared, there's nothing we
-            # can do, so just log nothing.
+            # PYTHON-1266. If our logger has disappeared (e.g. during
+            # interpreter shutdown), there's nothing we can do, so just
+            # log nothing.
             pass
 
     def add_timer(self, timer):

cassandra/metadata.py

@@ -2270,7 +2270,7 @@ def _build_table_metadata(self, row, col_rows=None, trigger_rows=None):
 
                     # Some thrift tables define names in composite types (see PYTHON-192)
                     if not column_aliases and hasattr(comparator, 'fieldnames'):
-                        column_aliases = filter(None, comparator.fieldnames)
+                        column_aliases = list(filter(None, comparator.fieldnames))
             else:
                 is_compact = True
                 if column_aliases or not col_rows or is_dct_comparator:

cassandra/util.py

@@ -810,7 +810,8 @@ def __str__(self):
 inet_ntop = socket.inet_ntop
 
 
-# similar to collections.namedtuple, reproduced here because Python 2.6 did not have the rename logic
+# similar to collections.namedtuple, reproduced here to handle invalid identifiers
+# by renaming them to positional names
 def _positional_rename_invalid_identifiers(field_names):
     names_out = list(field_names)
     for index, name in enumerate(field_names):
@@ -1498,7 +1499,7 @@ class Version(object):
     Internal minimalist class to compare versions.
     A valid version is: <int>.<int>.<int>.<int or str>.
 
-    TODO: when python2 support is removed, use packaging.version.
+    TODO: consider using packaging.version instead.
     """
 
     _version = None