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/oeb/stylizer.py

@@ -10,17 +10,16 @@ from css_parser.css import (CSSStyleRule, CSSPageRule, CSSFontFaceRule,
         cssproperties)
 from css_parser import (profile as cssprofiles, parseString, parseStyle, log as
         css_parser_log, CSSParser, profiles, replaceUrls)
+
+from ebook_converter import constants as const
 from ebook_converter import force_unicode, as_unicode
 from ebook_converter.ebooks import unit_convert
-from ebook_converter.ebooks.oeb.base import XHTML, XHTML_NS, CSS_MIME, OEB_STYLES, xpath, urlnormalize
+from ebook_converter.ebooks.oeb import base
 from ebook_converter.ebooks.oeb.normalize_css import DEFAULTS, normalizers
 from ebook_converter.css_selectors import Select, SelectorError, INAPPROPRIATE_PSEUDO_CLASSES
 from ebook_converter.tinycss.media3 import CSSMedia3Parser
 
 
-__license__ = 'GPL v3'
-__copyright__ = '2008, Marshall T. Vandegrift <llasram@gmail.com>'
-
 css_parser_log.setLevel(logging.WARN)
 
 _html_css_stylesheet = None
@@ -208,7 +207,7 @@ class Stylizer(object):
         stylesheets = [html_css_stylesheet()]
         if base_css:
             stylesheets.append(parseString(base_css, validate=False))
-        style_tags = xpath(tree, '//*[local-name()="style" or local-name()="link"]')
+        style_tags = base.xpath(tree, '//*[local-name()="style" or local-name()="link"]')
 
         # Add css_parser parsing profiles from output_profile
         for profile in self.opts.output_profile.extra_css_modules:
@@ -219,7 +218,7 @@ class Stylizer(object):
         parser = CSSParser(fetcher=self._fetch_css_file,
                 log=logging.getLogger('calibre.css'))
         for elem in style_tags:
-            if (elem.tag == XHTML('style') and elem.get('type', CSS_MIME) in OEB_STYLES and media_ok(elem.get('media'))):
+            if (elem.tag == base.tag('xhtml', 'style') and elem.get('type', base.CSS_MIME) in base.OEB_STYLES and media_ok(elem.get('media'))):
                 text = elem.text if elem.text else ''
                 for x in elem:
                     t = getattr(x, 'text', None)
@@ -245,7 +244,7 @@ class Stylizer(object):
                                 self.logger.warn('Ignoring missing stylesheet in @import rule:', rule.href)
                                 continue
                             sitem = hrefs[ihref]
-                            if sitem.media_type not in OEB_STYLES:
+                            if sitem.media_type not in base.OEB_STYLES:
                                 self.logger.warn('CSS @import of non-CSS file %r' % rule.href)
                                 continue
                             stylesheets.append(sitem.data)
@@ -254,11 +253,11 @@ class Stylizer(object):
                     replaceUrls(stylesheet, item.abshref,
                             ignoreImportRules=True)
                     stylesheets.append(stylesheet)
-            elif (elem.tag == XHTML('link') and elem.get('href') and elem.get(
+            elif (elem.tag == base.tag('xhtml', 'link') and elem.get('href') and elem.get(
                     'rel', 'stylesheet').lower() == 'stylesheet' and elem.get(
-                    'type', CSS_MIME).lower() in OEB_STYLES and media_ok(elem.get('media'))
+                    'type', base.CSS_MIME).lower() in base.OEB_STYLES and media_ok(elem.get('media'))
                 ):
-                href = urlnormalize(elem.attrib['href'])
+                href = base.urlnormalize(elem.attrib['href'])
                 path = item.abshref(href)
                 sitem = oeb.manifest.hrefs.get(path, None)
                 if sitem is None:
@@ -326,7 +325,8 @@ class Stylizer(object):
 
                                 special_text = ''.join(punctuation_chars) + \
                                         (text[0] if text else '')
-                                span = x.makeelement('{%s}span' % XHTML_NS)
+                                span = x.makeelement('{%s}span' %
+                                                     const.XHTML_NS)
                                 span.text = special_text
                                 span.set('data-fake-first-letter', '1')
                                 span.tail = text[1:]
@@ -340,10 +340,10 @@ class Stylizer(object):
             else:
                 for elem in matches:
                     self.style(elem)._update_cssdict(cssdict)
-        for elem in xpath(tree, '//h:*[@style]'):
+        for elem in base.xpath(tree, '//h:*[@style]'):
             self.style(elem)._apply_style_attr(url_replacer=item.abshref)
         num_pat = re.compile(r'[0-9.]+$')
-        for elem in xpath(tree, '//h:img[@width or @height]'):
+        for elem in base.xpath(tree, '//h:img[@width or @height]'):
             style = self.style(elem)
             # Check if either height or width is not default
             is_styled = style._style.get('width', 'auto') != 'auto' or \
@@ -370,7 +370,7 @@ class Stylizer(object):
             self.logger.warn('CSS import of missing file %r' % path)
             return (None, None)
         item = hrefs[path]
-        if item.media_type not in OEB_STYLES:
+        if item.media_type not in base.OEB_STYLES:
             self.logger.warn('CSS import of non-CSS file %r' % path)
             return (None, None)
         data = item.data.cssText