Remove python2 support for core build tools

Depedencies on Python2/3 cross support (such as six, past and future)
are removed as only Python3 is supported at this point. Fewer
external deps is a good thing.

Signed-off-by: Ben Leslie <benno@brkawy.com>
Signed-off-by: Ivan Velickovic <i.velickovic@unsw.edu.au>

tools/bitfield_gen.py

@@ -13,7 +13,6 @@
 # See bitfield_gen.md for syntax, examples, and more information.
 ##
 
-from __future__ import print_function, division
 import sys
 import os.path
 import optparse
@@ -21,7 +20,6 @@ import re
 import itertools
 import tempfile
 
-from six.moves import range
 from functools import reduce
 
 import lex

tools/lex.py

@@ -36,35 +36,18 @@
 __version__ = "3.2"
 __tabversion__ = "3.2"       # Version of table file used
 
-from past.builtins import cmp
 import re
 import sys
 import types
 import copy
 import os
 
-# Python3 doesn't have a build-in cmp function.
+StringTypes = (str, bytes)
-# We need to import it here, even though it isn't called in this file
-# when interpreted by python3, to prevent pylint from treating it as
-# an error.
 
-# This tuple contains known string types
-try:
-    # Python 2.6
-    StringTypes = (types.StringType, types.UnicodeType)
-except AttributeError:
-    # Python 3.0
-    StringTypes = (str, bytes)
 
-# Extract the code attribute of a function. Different implementations
+def func_code(f):
-# are for Python 2/3 compatibility.
+    return f.__code__
 
-if sys.version_info[0] < 3:
-    def func_code(f):
-        return f.func_code
-else:
-    def func_code(f):
-        return f.__code__
 
 # This regular expression is used to match valid token names
 _is_identifier = re.compile(r'^[a-zA-Z0-9_]+$')

tools/umm.py

@@ -5,9 +5,7 @@
 # SPDX-License-Identifier: BSD-2-Clause
 #
 
-from __future__ import print_function
 import sys
-import six
 from functools import reduce
 
 # We assume length tp > 0
@@ -119,7 +117,7 @@ def print_graph(filename, out_file):
     mp = build_types(filename)
 
     print('digraph types {', file=out_file)
-    for k, flds in six.iteritems(mp):
+    for k, flds in mp.iteritems():
         for fld, tp in flds:
             # if is_base(tp):
             print('\t "%s" -> "%s" [label="%s"]' % (k, base_name(tp), fld),