Use the real constants module.

This is progressing refactor of the calibre code to make it more
readable, and transform it to something more coherent.

In this patch, there are changes regarding imports for some modules,
instead of polluting namespace of each module with some other modules
symbols, which often were imported from other modules. Yuck.

ebook_converter/ebooks/docx/writer/from_html.py

@@ -1,22 +1,19 @@
+import collections
 import re
-from collections import Counter
 
 from ebook_converter.ebooks.docx.writer.container import create_skeleton, page_size, page_effective_area
-from ebook_converter.ebooks.docx.writer.styles import StylesManager, FloatSpec
-from ebook_converter.ebooks.docx.writer.links import LinksManager
-from ebook_converter.ebooks.docx.writer.images import ImagesManager
 from ebook_converter.ebooks.docx.writer.fonts import FontsManager
-from ebook_converter.ebooks.docx.writer.tables import Table
+from ebook_converter.ebooks.docx.writer.images import ImagesManager
+from ebook_converter.ebooks.docx.writer.links import LinksManager
 from ebook_converter.ebooks.docx.writer.lists import ListsManager
+from ebook_converter.ebooks.docx.writer.styles import StylesManager, FloatSpec
+from ebook_converter.ebooks.docx.writer.tables import Table
+from ebook_converter.ebooks.oeb import base
+from ebook_converter.ebooks.oeb import parse_utils
 from ebook_converter.ebooks.oeb.stylizer import Stylizer as Sz, Style as St
-from ebook_converter.ebooks.oeb.base import XPath, barename
 from ebook_converter.utils.localization import lang_as_iso639_1
 
 
-__license__ = 'GPL v3'
-__copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
-
-
 def lang_for_tag(tag):
     for attr in ('lang', '{http://www.w3.org/XML/1998/namespace}lang'):
         val = lang_as_iso639_1(tag.get(attr))
@@ -140,7 +137,7 @@ class Block(object):
         self.numbering_id = None
         self.parent_items = None
         self.html_block = html_block
-        self.html_tag = barename(html_block.tag)
+        self.html_tag = parse_utils.barename(html_block.tag)
         self.float_spec = float_spec
         if float_spec is not None:
             float_spec.blocks.append(self)
@@ -387,7 +384,7 @@ class Blocks(object):
     def resolve_language(self):
         default_lang = self.styles_manager.document_lang
         for block in self.all_blocks:
-            count = Counter()
+            count = collections.Counter()
             for run in block.runs:
                 count[run.lang] += 1
             if count:
@@ -473,13 +470,13 @@ class Convert(object):
         self.abshref = self.images_manager.abshref = item.abshref
 
         self.current_lang = lang_for_tag(item.data) or self.styles_manager.document_lang
-        for i, body in enumerate(XPath('//h:body')(item.data)):
+        for i, body in enumerate(base.XPath('//h:body')(item.data)):
             with self.blocks:
                 self.blocks.top_bookmark = self.links_manager.bookmark_for_anchor(self.links_manager.top_anchor, self.current_item, body)
                 self.process_tag(body, stylizer, is_first_tag=i == 0)
 
     def process_tag(self, html_tag, stylizer, is_first_tag=False, float_spec=None):
-        tagname = barename(html_tag.tag)
+        tagname = parse_utils.barename(html_tag.tag)
         tag_style = stylizer.style(html_tag)
         ignore_tag_contents = tagname in {'script', 'style', 'title', 'meta'} or tag_style.is_hidden
         display = tag_style._get('display')
@@ -573,7 +570,7 @@ class Convert(object):
             text = html_tag.text
             if text:
                 block.add_text(text, tag_style, ignore_leading_whitespace=True, is_parent_style=True, link=self.current_link, lang=self.current_lang)
-            elif tagname == 'li' and len(html_tag) and barename(html_tag[0].tag) in ('ul', 'ol') and len(html_tag[0]):
+            elif tagname == 'li' and len(html_tag) and parse_utils.barename(html_tag[0].tag) in ('ul', 'ol') and len(html_tag[0]):
                 block.force_not_empty = True
 
     def add_inline_tag(self, tagname, html_tag, tag_style, stylizer):