diff --git a/fanficfare/mobi.py b/fanficfare/mobi.py
index 76bae5e8..adc95096 100644
--- a/fanficfare/mobi.py
+++ b/fanficfare/mobi.py
@@ -1,13 +1,18 @@
 #!/usr/bin/python
 # Copyright(c) 2009 Andrew Chatham and Vijay Pandurangan
+# Changes Copyright 2018 FanFicFare team
 
     
-from six import StringIO
 import struct
 import time
 import random
 import logging
 
+# py2 vs py3 transition
+from six import text_type as unicode
+from six import string_types as basestring
+from six import BytesIO # StringIO under py2
+
 logger = logging.getLogger(__name__)
 
 from mobihtml import HtmlProcessor
@@ -57,12 +62,12 @@ class Converter:
     self._refresh_url = refresh_url
 
   def ConvertString(self, s):
-    out = StringIO.StringIO()
+    out = BytesIO()
     self._ConvertStringToFile(s, out)
     return out.getvalue()
 
   def ConvertStrings(self, html_strs):
-    out = StringIO.StringIO()
+    out = BytesIO()
     self._ConvertStringsToFile(html_strs, out)
     return out.getvalue()
 
@@ -126,6 +131,7 @@ class Converter:
       tmp = self.MakeOneHTML(html_strs)
       self._ConvertStringToFile(tmp, out_file)
     except Exception as e:
+      raise
       logger.error('Error %s', e)
       #logger.debug('Details: %s' % html_strs)
 
diff --git a/fanficfare/mobihtml.py b/fanficfare/mobihtml.py
index 7782a43c..c0dcf029 100644
--- a/fanficfare/mobihtml.py
+++ b/fanficfare/mobihtml.py
@@ -5,8 +5,11 @@
 
 import re
 import sys
-from six import StringIO
-from six.moves import urllib
+from six.moves.urllib.parse import unquote
+
+# py2 vs py3 transition
+from six import text_type as unicode
+from six import binary_type as bytes
 
 # import bs4
 # BeautifulSoup = bs4.BeautifulSoup
@@ -55,14 +58,14 @@ class HtmlProcessor:
 
     # str() instead of unicode() rather than figure out how to fix
     # ancient mobi.py code.
-    assembled_text = str(self._soup)
+    assembled_text = unicode(self._soup)
 
     del self._soup # shouldn't touch this anymore
     for anchor_num, original_ref in self._anchor_references:
-      ref = urllib.unquote(original_ref[1:]) # remove leading '#'
+      ref = unquote(original_ref[1:]) # remove leading '#'
       # Find the position of ref in the utf-8 document.
       # TODO(chatham): Using regexes and looking for name= would be better.
-      newpos = assembled_text.rfind(ref.encode('utf-8'))
+      newpos = assembled_text.rfind(ref) # .encode('utf-8')
       if newpos == -1:
         print >>sys.stderr, 'Could not find anchor "%s"' % original_ref
         continue
diff --git a/fanficfare/writers/base_writer.py b/fanficfare/writers/base_writer.py
index 3e97a356..12eada78 100644
--- a/fanficfare/writers/base_writer.py
+++ b/fanficfare/writers/base_writer.py
@@ -21,11 +21,14 @@ import os.path
 import datetime
 import string
 import six
-from six import StringIO
 import zipfile
 from zipfile import ZipFile, ZIP_DEFLATED
 import logging
 
+# py2 vs py3 transition
+from six import text_type as unicode
+from six import BytesIO # StringIO under py2
+
 from ..configurable import Configurable
 from ..htmlcleanup import removeEntities, removeAllEntities, stripHTML
 
@@ -179,7 +182,7 @@ class BaseStoryWriter(Configurable):
             logger.info("Save directly to file: %s" % outfilename)
             if self.getConfig('make_directories'):
                 path=""
-                outputdirs = os.path.dirname(outfilename).split('/')
+                outputdirs = os.path.dirname(unicode(outfilename)).split('/')
                 for dir in outputdirs:
                     path+=dir+"/"
                     if not os.path.exists(path):
@@ -213,7 +216,7 @@ class BaseStoryWriter(Configurable):
                                                  # above, it will only
                                                  # fetch once.
         if self.getConfig('zip_output'):
-            out = StringIO()
+            out = BytesIO()
             self.zipout = ZipFile(outstream, 'w', compression=ZIP_DEFLATED)
             self.writeStoryImpl(out)
             self.zipout.writestr(self.getBaseFileName(),out.getvalue())
diff --git a/fanficfare/writers/writer_epub.py b/fanficfare/writers/writer_epub.py
index 8ecfeda0..93bad44f 100644
--- a/fanficfare/writers/writer_epub.py
+++ b/fanficfare/writers/writer_epub.py
@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 
-# Copyright 2011 Fanficdownloader team, 2017 FanFicFare team
+# Copyright 2011 Fanficdownloader team, 2018 FanFicFare team
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -15,14 +15,19 @@
 # limitations under the License.
 #
 
+from __future__ import absolute_import
 import logging
 import string
-from six import StringIO
 import zipfile
 from zipfile import ZipFile, ZIP_STORED, ZIP_DEFLATED
 import urllib
 import re
 
+# py2 vs py3 transition
+from six import text_type as unicode
+from six import string_types as basestring
+from six import BytesIO # StringIO under py2
+
 ## XML isn't as forgiving as HTML, so rather than generate as strings,
 ## use DOM to generate the XML files.
 from xml.dom.minidom import parse, parseString, getDOMImplementation
@@ -299,11 +304,11 @@ div { margin: 0pt; padding: 0pt; }
     def writeStoryImpl(self, out):
 
         ## Python 2.5 ZipFile is rather more primative than later
-        ## versions.  It can operate on a file, or on a StringIO, but
+        ## versions.  It can operate on a file, or on a BytesIO, but
         ## not on an open stream.  OTOH, I suspect we would have had
         ## problems with closing and opening again to change the
         ## compression type anyway.
-        zipio = StringIO()
+        zipio = BytesIO()
 
         ## mimetype must be first file and uncompressed.  Python 2.5
         ## ZipFile can't change compression type file-by-file, so we
@@ -518,8 +523,8 @@ div { margin: 0pt; padding: 0pt; }
                 COVER = string.Template(self.getConfig("cover_content"))
             else:
                 COVER = self.EPUB_COVER
-            coverIO = StringIO()
-            coverIO.write(COVER.substitute(dict(self.story.getAllMetadata().items()+{'coverimg':self.story.cover}.items())))
+            coverIO = BytesIO()
+            coverIO.write(COVER.substitute(dict(list(self.story.getAllMetadata().items())+list({'coverimg':self.story.cover}.items()))))
 
         if self.getConfig("include_titlepage"):
             items.append(("title_page","OEBPS/title_page.xhtml","application/xhtml+xml","Title Page"))
@@ -577,8 +582,10 @@ div { margin: 0pt; padding: 0pt; }
         contentxml = contentdom.toxml(encoding='utf-8')
 
         # tweak for brain damaged Nook STR.  Nook insists on name before content.
-        contentxml = contentxml.replace('<meta content="%s" name="cover"/>'%coverimgid,
-                                        '<meta name="cover" content="%s"/>'%coverimgid)
+        contentxml = unicode(contentxml).replace('<meta content="%s" name="cover"/>'%coverimgid,
+                                                 '<meta name="cover" content="%s"/>'%coverimgid)
+
+        
         outputepub.writestr("content.opf",contentxml)
 
         contentdom.unlink()
@@ -655,7 +662,7 @@ div { margin: 0pt; padding: 0pt; }
             outputepub.writestr("OEBPS/cover.xhtml",coverIO.getvalue())
             coverIO.close()
 
-        titlepageIO = StringIO()
+        titlepageIO = BytesIO()
         self.writeTitlePage(out=titlepageIO,
                             START=TITLE_PAGE_START,
                             ENTRY=TITLE_ENTRY,
@@ -667,7 +674,7 @@ div { margin: 0pt; padding: 0pt; }
         titlepageIO.close()
 
         # write toc page.
-        tocpageIO = StringIO()
+        tocpageIO = BytesIO()
         self.writeTOCPage(tocpageIO,
                           self.EPUB_TOC_PAGE_START,
                           self.EPUB_TOC_ENTRY,
@@ -678,7 +685,7 @@ div { margin: 0pt; padding: 0pt; }
 
         if dologpage:
             # write log page.
-            logpageIO = StringIO()
+            logpageIO = BytesIO()
             self.writeLogPage(logpageIO)
             outputepub.writestr("OEBPS/log_page.xhtml",logpageIO.getvalue())
             logpageIO.close()
diff --git a/fanficfare/writers/writer_mobi.py b/fanficfare/writers/writer_mobi.py
index 97fdfcbc..ec7a2599 100644
--- a/fanficfare/writers/writer_mobi.py
+++ b/fanficfare/writers/writer_mobi.py
@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 
-# Copyright 2011 Fanficdownloader team, 2015 FanFicFare team
+# Copyright 2011 Fanficdownloader team, 2018 FanFicFare team
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -15,15 +15,21 @@
 # limitations under the License.
 #
 
+from __future__ import absolute_import
 import logging
 import string
-from six import StringIO
 
 from .base_writer import *
 from ..htmlcleanup import stripHTML
 from ..mobi import Converter
 from ..exceptions import FailedToWriteOutput
 
+# py2 vs py3 transition
+from six import text_type as unicode
+from six import string_types as basestring
+from six import binary_type as bytes
+from six import BytesIO # StringIO under py2
+
 logger = logging.getLogger(__name__)
 
 class MobiWriter(BaseStoryWriter):
@@ -128,7 +134,7 @@ ${value}<br />
             NO_TITLE_ENTRY    = self.MOBI_NO_TITLE_ENTRY
             TITLE_PAGE_END    = self.MOBI_TITLE_PAGE_END
         
-        titlepageIO = StringIO.StringIO()
+        titlepageIO = BytesIO()
         self.writeTitlePage(out=titlepageIO,
                             START=TITLE_PAGE_START,
                             ENTRY=TITLE_ENTRY,
@@ -142,7 +148,7 @@ ${value}<br />
         ## MOBI always has a TOC injected by mobi.py because there's
         ## no meta-data TOC.
         # # write toc page.  
-        # tocpageIO = StringIO.StringIO()
+        # tocpageIO = BytesIO()
         # self.writeTOCPage(tocpageIO,
         #                   self.MOBI_TOC_PAGE_START,
         #                   self.MOBI_TOC_ENTRY,