diff --git a/m2r.py b/m2r.py
index a4e43c2..6c1e6e0 100644
--- a/m2r.py
+++ b/m2r.py
@@ -5,21 +5,13 @@
 import os
 import os.path
 import re
-import sys
 from argparse import ArgumentParser, Namespace
 
 from docutils import statemachine, nodes, io, utils
 from docutils.parsers import rst
-from docutils.core import ErrorString
-from docutils.utils import SafeString, column_width
+from docutils.utils import column_width
 import mistune
-
-if sys.version_info < (3, ):
-    from codecs import open as _open
-    from urlparse import urlparse
-else:
-    _open = open
-    from urllib.parse import urlparse
+from urllib.parse import urlparse
 
 __version__ = '0.2.1'
 _is_sphinx = False
@@ -609,10 +601,10 @@ def run(self):
             raise self.severe('Problems with "%s" directive path:\n'
                               'Cannot encode input file path "%s" '
                               '(wrong locale?).' %
-                              (self.name, SafeString(path)))
+                              (self.name, path))
         except IOError as error:
             raise self.severe('Problems with "%s" directive path:\n%s.' %
-                              (self.name, ErrorString(error)))
+                              (self.name, io.error_string(error)))
 
         # read from the file
         startline = self.options.get('start-line', None)
@@ -625,7 +617,7 @@ def run(self):
                 rawtext = include_file.read()
         except UnicodeError as error:
             raise self.severe('Problem with "%s" directive:\n%s' %
-                              (self.name, ErrorString(error)))
+                              (self.name, io.error_string(error)))
 
         config = self.state.document.settings.env.config
         converter = M2R(
@@ -670,7 +662,7 @@ def convert(text, **kwargs):
 def parse_from_file(file, encoding='utf-8', **kwargs):
     if not os.path.exists(file):
         raise OSError('No such file exists: {}'.format(file))
-    with _open(file, encoding=encoding) as f:
+    with open(file, encoding=encoding) as f:
         src = f.read()
     output = convert(src, **kwargs)
     return output
@@ -684,7 +676,7 @@ def save_to_file(file, src, encoding='utf-8', **kwargs):
         if confirm.upper() not in ('Y', 'YES'):
             print('skip {}'.format(file))
             return
-    with _open(target, 'w', encoding=encoding) as f:
+    with open(target, 'w', encoding=encoding) as f:
         f.write(src)
 
 
diff --git a/setup.py b/setup.py
index a5768ad..bbc01b0 100644
--- a/setup.py
+++ b/setup.py
@@ -1,7 +1,6 @@
 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
 
-import sys
 from os import path
 
 try:
@@ -19,8 +18,6 @@
 
 install_requires = ['mistune', 'docutils']
 test_requirements = ['pygments']
-if sys.version_info < (3, 3):
-    test_requirements.append('mock')
 
 setup(
     name='m2r',
@@ -42,12 +39,8 @@
         'Intended Audience :: Developers',
         'License :: OSI Approved :: MIT License',
         'Natural Language :: English',
-        'Programming Language :: Python :: 2',
-        'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.4',
-        'Programming Language :: Python :: 3.5',
-        'Programming Language :: Python :: 3.6',
+        'Programming Language :: Python :: 3.7',
         'Topic :: Text Processing',
     ],
     install_requires=install_requires,