diff --git a/notebook/config_manager.py b/notebook/config_manager.py
index 584df8870..a15c2454b 100644
--- a/notebook/config_manager.py
+++ b/notebook/config_manager.py
@@ -11,7 +11,6 @@ import json
 import os
 import copy
 
-from six import PY3
 from traitlets.config import LoggingConfigurable
 from traitlets.traitlets import Unicode, Bool
 
@@ -119,10 +118,7 @@ class BaseJSONConfigManager(LoggingConfigurable):
         # in order to avoid writing half-finished corrupted data to disk.
         json_content = json.dumps(data, indent=2)
 
-        if PY3:
-            f = io.open(filename, 'w', encoding='utf-8')
-        else:
-            f = open(filename, 'wb')
+        f = io.open(filename, 'w', encoding='utf-8')
         with f:
             f.write(json_content)
 
diff --git a/notebook/jstest.py b/notebook/jstest.py
index 0e531f64f..6849c9fd0 100644
--- a/notebook/jstest.py
+++ b/notebook/jstest.py
@@ -23,32 +23,16 @@ import time
 from io import BytesIO
 from threading import Thread, Lock, Event
 
-try:
-    from unittest.mock import patch
-except ImportError:
-    from mock import patch # py3
+from unittest.mock import patch
 
 from jupyter_core.paths import jupyter_runtime_dir
 from ipython_genutils.py3compat import bytes_to_str, which
 from notebook._sysinfo import get_sys_info
 from ipython_genutils.tempdir import TemporaryDirectory
 
-try:
-    # Python >= 3.3
-    from subprocess import TimeoutExpired
-    def popen_wait(p, timeout):
-        return p.wait(timeout)
-except ImportError:
-    class TimeoutExpired(Exception):
-        pass
-    def popen_wait(p, timeout):
-        """backport of Popen.wait from Python 3"""
-        for i in range(int(10 * timeout)):
-            if p.poll() is not None:
-                return
-            time.sleep(0.1)
-        if p.poll() is None:
-            raise TimeoutExpired
+from subprocess import TimeoutExpired
+def popen_wait(p, timeout):
+    return p.wait(timeout)
 
 NOTEBOOK_SHUTDOWN_TIMEOUT = 10
 
diff --git a/notebook/nbextensions.py b/notebook/nbextensions.py
index a6b5400e4..c6dad116b 100644
--- a/notebook/nbextensions.py
+++ b/notebook/nbextensions.py
@@ -13,13 +13,8 @@ import tarfile
 import zipfile
 from os.path import basename, join as pjoin, normpath
 
-try:
-    from urllib.parse import urlparse  # Py3
-    from urllib.request import urlretrieve
-except ImportError:
-    from urlparse import urlparse
-    from urllib import urlretrieve
-
+from urllib.parse import urlparse
+from urllib.request import urlretrieve
 from jupyter_core.paths import (
     jupyter_data_dir, jupyter_config_path, jupyter_path,
     SYSTEM_JUPYTER_PATH, ENV_JUPYTER_PATH,
diff --git a/notebook/notebookapp.py b/notebook/notebookapp.py
index faebd884e..6eba37308 100755
--- a/notebook/notebookapp.py
+++ b/notebook/notebookapp.py
@@ -32,10 +32,7 @@ import time
 import warnings
 import webbrowser
 
-try: #PY3
-    from base64 import encodebytes
-except ImportError: #PY2
-    from base64 import encodestring as encodebytes
+from base64 import encodebytes
 
 
 from jinja2 import Environment, FileSystemLoader
@@ -71,10 +68,7 @@ from notebook import (
 )
 
 # py23 compatibility
-try:
-    raw_input = raw_input
-except NameError:
-    raw_input = input
+raw_input = input
 
 from .base.handlers import Template404, RedirectWithParams
 from .log import log_request
diff --git a/notebook/utils.py b/notebook/utils.py
index 5d9815476..69f3586f1 100644
--- a/notebook/utils.py
+++ b/notebook/utils.py
@@ -16,13 +16,8 @@ import sys
 from distutils.version import LooseVersion
 
 
-try:
-    from urllib.parse import quote, unquote, urlparse, urljoin
-    from urllib.request import pathname2url
-except ImportError:
-    from urllib import quote, unquote, pathname2url
-    from urlparse import urlparse, urljoin
-
+from urllib.parse import quote, unquote, urlparse, urljoin
+from urllib.request import pathname2url
 # tornado.concurrent.Future is asyncio.Future
 # in tornado >=5 with Python 3
 from tornado.concurrent import Future as TornadoFuture