python3: apply various fixes from python-modernize "dict_six"

Imports were then fixed and consolidated to derive from the internal
polyglot.builtins

src/tinycss/__init__.py

@@ -17,6 +17,8 @@ from tinycss.page3 import CSSPage3Parser
 from tinycss.fonts3 import CSSFonts3Parser
 from tinycss.media3 import CSSMedia3Parser
 
+from polyglot.builtins import iterkeys
+
 
 PARSER_MODULES = {
     'page3': CSSPage3Parser,
@@ -47,5 +49,5 @@ def make_parser(*features, **kwargs):
 
 def make_full_parser(**kwargs):
     ''' A parser that parses all supported CSS 3 modules in addition to CSS 2.1 '''
-    features = tuple(PARSER_MODULES.iterkeys())
+    features = tuple(iterkeys(PARSER_MODULES))
     return make_parser(*features, **kwargs)

src/tinycss/tests/fonts3.py

@@ -9,6 +9,8 @@ __copyright__ = '2014, Kovid Goyal <kovid at kovidgoyal.net>'
 from tinycss.fonts3 import CSSFonts3Parser, parse_font_family, parse_font, serialize_font
 from tinycss.tests import BaseTest
 
+from polyglot.builtins import iteritems
+
 class TestFonts3(BaseTest):
 
     def test_font_face(self):
@@ -30,7 +32,7 @@ class TestFonts3(BaseTest):
 
     def test_parse_font_family(self):
         ' Test parsing of font-family values '
-        for raw, q in {
+        for raw, q in iteritems({
                 '"1as"': ['1as'],
                 'A B C, serif': ['A B C', 'serif'],
                 r'Red\/Black': ['Red/Black'],
@@ -43,14 +45,14 @@ class TestFonts3(BaseTest):
                 'A B, C D, "E", serif': ['A B', 'C D', 'E', 'serif'],
                 '': [],
                 '"", a': ['a'],
-        }.iteritems():
+        }):
             self.ae(q, parse_font_family(raw))
         for single in ('serif', 'sans-serif', 'A B C'):
             self.ae([single], parse_font_family(single))
 
     def test_parse_font(self):
         def t(raw, **kw):
-            q = {('line' if k == 'height' else 'font') + '-' + k:v for k, v in kw.iteritems()}
+            q = {('line' if k == 'height' else 'font') + '-' + k:v for k, v in iteritems(kw)}
             self.ae(q, parse_font(raw))
             self.ae(q, parse_font(serialize_font(q)))
         t('caption', family=['sans-serif'])