diff --git a/oauth2client/_openssl_crypt.py b/oauth2client/_openssl_crypt.py
index aca3505..d024cf3 100644
--- a/oauth2client/_openssl_crypt.py
+++ b/oauth2client/_openssl_crypt.py
@@ -14,7 +14,7 @@
 """OpenSSL Crypto-related routines for oauth2client."""
 
 import base64
-import six
+
 from OpenSSL import crypto
 
 from oauth2client._helpers import _parse_pem_key
diff --git a/oauth2client/_pycrypto_crypt.py b/oauth2client/_pycrypto_crypt.py
index fa02575..7b277aa 100644
--- a/oauth2client/_pycrypto_crypt.py
+++ b/oauth2client/_pycrypto_crypt.py
@@ -17,7 +17,6 @@ from Crypto.PublicKey import RSA
 from Crypto.Hash import SHA256
 from Crypto.Signature import PKCS1_v1_5
 from Crypto.Util.asn1 import DerSequence
-import six
 
 from oauth2client._helpers import _parse_pem_key
 from oauth2client._helpers import _to_bytes
diff --git a/oauth2client/appengine.py b/oauth2client/appengine.py
index 47d390c..fcbef3e 100644
--- a/oauth2client/appengine.py
+++ b/oauth2client/appengine.py
@@ -32,7 +32,7 @@ from google.appengine.api import memcache
 from google.appengine.api import users
 from google.appengine.ext import db
 from google.appengine.ext.webapp.util import login_required
-from google.appengine.ext.webapp.util import run_wsgi_app
+
 from oauth2client import GOOGLE_AUTH_URI
 from oauth2client import GOOGLE_REVOKE_URI
 from oauth2client import GOOGLE_TOKEN_URI
diff --git a/oauth2client/client.py b/oauth2client/client.py
index c2efa38..cd5959f 100644
--- a/oauth2client/client.py
+++ b/oauth2client/client.py
@@ -41,7 +41,6 @@ from oauth2client import GOOGLE_TOKEN_INFO_URI
 from oauth2client._helpers import _from_bytes
 from oauth2client._helpers import _to_bytes
 from oauth2client._helpers import _urlsafe_b64decode
-from oauth2client._helpers import _urlsafe_b64encode
 from oauth2client import clientsecrets
 from oauth2client import util
 
@@ -1106,7 +1105,10 @@ def _in_gae_environment():
         return SETTINGS.env_name in ('GAE_PRODUCTION', 'GAE_LOCAL')
 
     try:
-        import google.appengine
+        import google.appengine  # noqa: unused import
+    except ImportError:
+        pass
+    else:
         server_software = os.environ.get(_SERVER_SOFTWARE, '')
         if server_software.startswith('Google App Engine/'):
             SETTINGS.env_name = 'GAE_PRODUCTION'
@@ -1114,8 +1116,6 @@ def _in_gae_environment():
         elif server_software.startswith('Development/'):
             SETTINGS.env_name = 'GAE_LOCAL'
             return True
-    except ImportError:
-        pass
 
     return False
 
diff --git a/oauth2client/util.py b/oauth2client/util.py
index 352afd8..1150e2b 100644
--- a/oauth2client/util.py
+++ b/oauth2client/util.py
@@ -20,8 +20,6 @@
 import functools
 import inspect
 import logging
-import sys
-import types
 
 import six
 from six.moves import urllib
diff --git a/oauth2client/xsrfutil.py b/oauth2client/xsrfutil.py
index 685eb46..10bbe3f 100644
--- a/oauth2client/xsrfutil.py
+++ b/oauth2client/xsrfutil.py
@@ -18,7 +18,6 @@
 import base64
 import binascii
 import hmac
-import six
 import time
 
 from oauth2client._helpers import _to_bytes
diff --git a/scripts/fetch_gae_sdk.py b/scripts/fetch_gae_sdk.py
index 49d380a..24a6db5 100755
--- a/scripts/fetch_gae_sdk.py
+++ b/scripts/fetch_gae_sdk.py
@@ -13,7 +13,6 @@ import json
 import os
 import StringIO
 import sys
-import tempfile
 import urllib2
 import zipfile
 
diff --git a/tests/http_mock.py b/tests/http_mock.py
index 664a93d..6053299 100644
--- a/tests/http_mock.py
+++ b/tests/http_mock.py
@@ -14,8 +14,6 @@
 
 """Copy of googleapiclient.http's mock functionality."""
 
-import json
-
 import httplib2
 
 # TODO(craigcitro): Find a cleaner way to share this code with googleapiclient.
diff --git a/tests/test_appengine.py b/tests/test_appengine.py
index f9a52f8..a20ddfe 100644
--- a/tests/test_appengine.py
+++ b/tests/test_appengine.py
@@ -44,7 +44,6 @@ from google.appengine.api.memcache import memcache_stub
 from google.appengine.ext import db
 from google.appengine.ext import ndb
 from google.appengine.ext import testbed
-from google.appengine.runtime import apiproxy_errors
 from oauth2client import appengine
 from oauth2client import GOOGLE_TOKEN_URI
 from oauth2client.clientsecrets import _loadfile
@@ -60,7 +59,6 @@ from oauth2client.appengine import StorageByKeyName
 from oauth2client.client import _CLOUDSDK_CONFIG_ENV_VAR
 from oauth2client.client import AccessTokenRefreshError
 from oauth2client.client import Credentials
-from oauth2client.client import FlowExchangeError
 from oauth2client.client import OAuth2Credentials
 from oauth2client.client import flow_from_clientsecrets
 from oauth2client.client import save_to_well_known_file
diff --git a/tests/test_clientsecrets.py b/tests/test_clientsecrets.py
index 9e3c1b6..2dd1a01 100644
--- a/tests/test_clientsecrets.py
+++ b/tests/test_clientsecrets.py
@@ -19,8 +19,6 @@ import os
 import tempfile
 import unittest
 
-import httplib2
-
 from oauth2client._helpers import _from_bytes
 from oauth2client import GOOGLE_AUTH_URI
 from oauth2client import GOOGLE_REVOKE_URI
diff --git a/tests/test_crypt.py b/tests/test_crypt.py
index d8c5964..aec703d 100644
--- a/tests/test_crypt.py
+++ b/tests/test_crypt.py
@@ -14,7 +14,6 @@
 
 import base64
 import os
-import sys
 import unittest
 
 import mock
diff --git a/tests/test_django_orm.py b/tests/test_django_orm.py
index d0a3502..ae32e78 100644
--- a/tests/test_django_orm.py
+++ b/tests/test_django_orm.py
@@ -37,7 +37,6 @@ django_settings.SECRET_KEY = 'xyzzy'
 from django.db import models
 
 from oauth2client._helpers import _from_bytes
-from oauth2client._helpers import _to_bytes
 from oauth2client.client import Credentials
 from oauth2client.client import Flow
 from oauth2client.client import OAuth2Credentials
diff --git a/tests/test_gce.py b/tests/test_gce.py
index 7a3e558..a12907b 100644
--- a/tests/test_gce.py
+++ b/tests/test_gce.py
@@ -21,7 +21,6 @@ import json
 from six.moves import urllib
 import unittest
 
-import httplib2
 import mock
 
 from oauth2client._helpers import _to_bytes
diff --git a/tests/test_jwt.py b/tests/test_jwt.py
index b304e2e..72ebba4 100644
--- a/tests/test_jwt.py
+++ b/tests/test_jwt.py
@@ -20,14 +20,11 @@ Unit tests for oauth2client.
 """
 
 import os
-import mock
-import sys
 import tempfile
 import time
 import unittest
 
 from .http_mock import HttpMockSequence
-from oauth2client import client
 from oauth2client.client import Credentials
 from oauth2client.client import SignedJwtAssertionCredentials
 from oauth2client.client import VerifyJwtTokenError