Removed polyglots unicode_type usage

ebook_converter/ebooks/oeb/polish/parsing.py

@@ -7,7 +7,6 @@ from ebook_converter import xml_replace_entities
 from ebook_converter.utils.xml_parse import safe_xml_fromstring
 from ebook_converter.ebooks.chardet import xml_to_unicode, strip_encoding_declarations
 from ebook_converter.utils.cleantext import clean_xml_chars
-from ebook_converter.polyglot.builtins import unicode_type
 
 
 __license__ = 'GPL v3'
@@ -81,7 +80,7 @@ def parse(raw, decoder=None, log=None, line_numbers=True, linenumber_attribute=N
         if linenumber_attribute:
             for elem in ans.iter(LxmlElement):
                 if elem.sourceline is not None:
-                    elem.set(linenumber_attribute, unicode_type(elem.sourceline))
+                    elem.set(linenumber_attribute, str(elem.sourceline))
         return ans
     except Exception:
         if log is not None: