diff --git a/manual/latex.py b/manual/latex.py
index 710883d440..517aed0adb 100644
--- a/manual/latex.py
+++ b/manual/latex.py
@@ -8,9 +8,9 @@ __docformat__ = 'restructuredtext en'
 
 import os
 
-
 from sphinx.builders.latex import LaTeXBuilder
 
+
 class LaTeXHelpBuilder(LaTeXBuilder):
     name = 'mylatex'
 
@@ -18,9 +18,9 @@ class LaTeXHelpBuilder(LaTeXBuilder):
         LaTeXBuilder.finish(self)
         self.info('Fixing Cyrillic characters...')
         tex = os.path.join(self.outdir, 'calibre.tex')
-        with open(tex, 'r+') as f:
-            raw = f.read()
+        with open(tex, 'r+b') as f:
+            raw = f.read().decode('utf-8')
             for x in (u'Михаил Горбачёв', u'Фёдор Миха́йлович Достоевский'):
                 raw = raw.replace(x, u'{\\fontencoding{T2A}\\selectfont %s}' % (x.replace(u'а́', u'a')))
             f.seek(0)
-            f.write(raw)
+            f.write(raw.encode('utf-8'))
diff --git a/src/calibre/ebooks/pdf/render/serialize.py b/src/calibre/ebooks/pdf/render/serialize.py
index 1af34ed9c5..c560f82eaa 100644
--- a/src/calibre/ebooks/pdf/render/serialize.py
+++ b/src/calibre/ebooks/pdf/render/serialize.py
@@ -278,7 +278,7 @@ class PDFStream(object):
         self.stream = HashingStream(stream)
         self.compress = compress
         self.write_line(PDFVER)
-        self.write_line(u'%íì¦"'.encode())
+        self.write_line(u'%íì¦"'.encode('utf-8'))
         creator = ('%s %s [https://calibre-ebook.com]'%(__appname__,
                                     __version__))
         self.write_line('%% Created by %s'%creator)
@@ -528,5 +528,3 @@ class PDFStream(object):
         self.write_line('startxref')
         self.write_line('%d'%startxref)
         self.stream.write('%%EOF')
-
-
diff --git a/src/calibre/ebooks/rtf2xml/tokenize.py b/src/calibre/ebooks/rtf2xml/tokenize.py
index bd86894393..e2933fbeb9 100755
--- a/src/calibre/ebooks/rtf2xml/tokenize.py
+++ b/src/calibre/ebooks/rtf2xml/tokenize.py
@@ -53,13 +53,13 @@ class Tokenize:
 
     def __unicode_process(self, token):
         # change scope in
-        if token == '\{':
+        if token == r'\{':
             self.__uc_value.append(self.__uc_value[-1])
             # basic error handling
             self.__reini_utf8_counters()
             return token
         # change scope out
-        elif token == '\}':
+        elif token == r'\}':
             self.__uc_value.pop()
             self.__reini_utf8_counters()
             return token
@@ -113,10 +113,10 @@ class Tokenize:
         input_file = self.__replace_spchar.mreplace(input_file)
         # this is for older RTF
         input_file = self.__par_exp.sub('\n\\par \n', input_file)
-        input_file = self.__cwdigit_exp.sub("\g<1>\n\g<2>", input_file)
-        input_file = self.__cs_ast.sub("\g<1>", input_file)
-        input_file = self.__ms_hex_exp.sub("\\mshex0\g<1> ", input_file)
-        input_file = self.__utf_ud.sub("\\{\\uc0 \g<1>\\}", input_file)
+        input_file = self.__cwdigit_exp.sub("\\g<1>\n\\g<2>", input_file)
+        input_file = self.__cs_ast.sub(r"\g<1>", input_file)
+        input_file = self.__ms_hex_exp.sub("\\mshex0\\g<1> ", input_file)
+        input_file = self.__utf_ud.sub("\\{\\uc0 \\g<1>\\}", input_file)
         # remove \n in bin data
         input_file = self.__bin_exp.sub(lambda x:
                                         x.group().replace('\n', '') + '\n', input_file)
diff --git a/src/calibre/gui2/__init__.py b/src/calibre/gui2/__init__.py
index 0ca558ad12..218714d498 100644
--- a/src/calibre/gui2/__init__.py
+++ b/src/calibre/gui2/__init__.py
@@ -23,7 +23,11 @@ from calibre.utils.date import UNDEFINED_DATE
 from calibre.utils.localization import get_lang
 from calibre.utils.file_type_icons import EXT_MAP
 
-NO_URL_FORMATTING = QUrl.None_
+try:
+    NO_URL_FORMATTING = QUrl.None_
+except AttributeError:
+    NO_URL_FORMATTING = getattr(QUrl, 'None')
+
 
 # Setup gprefs {{{
 gprefs = JSONConfig('gui')
diff --git a/src/calibre/gui2/book_details.py b/src/calibre/gui2/book_details.py
index 1811afd430..5d5d8ec9d6 100644
--- a/src/calibre/gui2/book_details.py
+++ b/src/calibre/gui2/book_details.py
@@ -57,7 +57,7 @@ def css():
         val = P('templates/book_details.css', data=True).decode('utf-8')
         col = QApplication.instance().palette().color(QPalette.Link).name()
         val = val.replace('LINK_COLOR', col)
-        _css = re.sub(r'/\*.*?\*/', '', val, flags=re.DOTALL)
+        _css = re.sub(unicode(r'/\*.*?\*/'), u'', val, flags=re.DOTALL)
     return _css
 
 
diff --git a/src/calibre/linux.py b/src/calibre/linux.py
index 25b63bf6f4..deed629ddb 100644
--- a/src/calibre/linux.py
+++ b/src/calibre/linux.py
@@ -387,7 +387,7 @@ _ebook_edit() {
         files)
             ebookfile=${~${(Q)line[1]}}
 
-            if [[ -f "$ebookfile" && "$ebookfile" =~ '\.[eE][pP][uU][bB]$' ]]; then
+            if [[ -f "$ebookfile" && "$ebookfile" =~ '\\.[eE][pP][uU][bB]$' ]]; then
                 _zip_cache_name="$ebookfile"
                 _zip_cache_list=( ${(f)"$(zipinfo -1 $_zip_cache_name 2>/dev/null)"} )
             else
diff --git a/src/calibre/srv/tests/http.py b/src/calibre/srv/tests/http.py
index 753f3dacd0..4d1360af17 100644
--- a/src/calibre/srv/tests/http.py
+++ b/src/calibre/srv/tests/http.py
@@ -39,7 +39,7 @@ class TestHTTP(BaseTest):
              '\r\n', a='one', b='two 2 3', c='three')
 
         test('Non-ascii headers parsing',
-             'a:mūs\r', '\r\n', a='mūs')
+             'a:mūs\r'.encode('utf-8'), '\r\n', a='mūs')
 
         test('Comma-separated parsing',
              'Accept-Encoding: one',