diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index c09f69ad69..ffe82a1ccf 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -11,6 +11,17 @@ details on the presubmit API built into depot_tools.
 
 def CommonChecks(input_api, output_api):
   results = []
+  import sys
+  if not sys.version.startswith('2.5'):
+    # Depot_tools has the particularity that it needs to be tested on python
+    # 2.5. But we don't want the presubmit check to fail if it is not installed.
+    results.append(output_api.PresubmitNotifyResult(
+        'You should install python 2.5 and run ln -s $(which python2.5) python.'
+        '\n'
+        'A great place to put this symlink is in depot_tools.\n'
+        'Otherwise, you break depot_tools on python 2.5, you get to keep the '
+        'pieces.'))
+
 
   results.extend(input_api.canned_checks.CheckOwners(input_api, output_api))
   black_list = list(input_api.DEFAULT_BLACK_LIST) + [
diff --git a/chrome-update.py b/chrome-update.py
index 3889361783..4f5731cb4d 100755
--- a/chrome-update.py
+++ b/chrome-update.py
@@ -1,5 +1,5 @@
-#!/usr/bin/python
-# Copyright (c) 2009 The Chromium Authors. All rights reserved.
+#!/usr/bin/env python
+# Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
diff --git a/drover.py b/drover.py
index abd942aa86..04fbd265a9 100755
--- a/drover.py
+++ b/drover.py
@@ -1,5 +1,5 @@
-#!/usr/bin/python
-# Copyright (c) 2010 The Chromium Authors. All rights reserved.
+#!/usr/bin/env python
+# Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
diff --git a/fix_encoding.py b/fix_encoding.py
index ab418695b2..87e54a5790 100644
--- a/fix_encoding.py
+++ b/fix_encoding.py
@@ -187,7 +187,8 @@ class WinUnicodeConsoleOutput(WinUnicodeOutputBase):
 
     # Loads the necessary function.
     from ctypes import byref, GetLastError, POINTER, windll, WINFUNCTYPE
-    from ctypes.wintypes import BOOL, DWORD, HANDLE, LPVOID, LPWSTR
+    from ctypes.wintypes import BOOL, DWORD, HANDLE, LPWSTR
+    from ctypes.wintypes import LPVOID  # pylint: disable=E0611
 
     self._DWORD = DWORD
     self._byref = byref
diff --git a/gcl.py b/gcl.py
index 76a217c442..6136d1c5a9 100755
--- a/gcl.py
+++ b/gcl.py
@@ -1,5 +1,5 @@
-#!/usr/bin/python
-# Copyright (c) 2010 The Chromium Authors. All rights reserved.
+#!/usr/bin/env python
+# Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
@@ -25,12 +25,8 @@ try:
   import simplejson as json  # pylint: disable=F0401
 except ImportError:
   try:
-    import json
-    # Some versions of python2.5 have an incomplete json module.  Check to make
-    # sure loads exists.
-    # pylint: disable=W0104
-    json.loads
-  except (ImportError, AttributeError):
+    import json  # pylint: disable=F0401
+  except ImportError:
     # Import the one included in depot_tools.
     sys.path.append(os.path.join(os.path.dirname(__file__), 'third_party'))
     import simplejson as json  # pylint: disable=F0401
diff --git a/gclient.py b/gclient.py
index c33973dfde..e63f85abd0 100644
--- a/gclient.py
+++ b/gclient.py
@@ -1,5 +1,5 @@
-#!/usr/bin/python
-# Copyright (c) 2010 The Chromium Authors. All rights reserved.
+#!/usr/bin/env python
+# Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
diff --git a/git_cl.py b/git_cl.py
index e22ea6afbc..1887cbb8da 100755
--- a/git_cl.py
+++ b/git_cl.py
@@ -1,7 +1,12 @@
-#!/usr/bin/python
-# git-cl -- a git-command for integrating reviews on Rietveld
+#!/usr/bin/env python
+# Copyright (c) 2011 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
 # Copyright (C) 2008 Evan Martin <martine@danga.com>
 
+"""A git-command for integrating reviews on Rietveld."""
+
 import errno
 import logging
 import optparse
@@ -23,7 +28,7 @@ try:
   import simplejson as json  # pylint: disable=F0401
 except ImportError:
   try:
-    import json
+    import json  # pylint: disable=F0401
   except ImportError:
     # Fall back to the packaged version.
     sys.path.append(os.path.join(os.path.dirname(__file__), 'third_party'))
diff --git a/owners.py b/owners.py
index 5aabb60077..5be7ff6d00 100644
--- a/owners.py
+++ b/owners.py
@@ -18,6 +18,8 @@ BASIC_EMAIL_REGEXP = r'^[\w\-\+\%\.]+\@[\w\-\+\%\.]+$'
 
 def _assert_is_collection(obj):
   assert not isinstance(obj, basestring)
+  # Module 'collections' has no 'Iterable' member
+  # pylint: disable=E1101
   if hasattr(collections, 'Iterable') and hasattr(collections, 'Sized'):
     assert (isinstance(obj, collections.Iterable) and
             isinstance(obj, collections.Sized))
diff --git a/presubmit_canned_checks.py b/presubmit_canned_checks.py
index 0e9d5da62f..a1144b8641 100644
--- a/presubmit_canned_checks.py
+++ b/presubmit_canned_checks.py
@@ -598,6 +598,7 @@ def RunPylint(input_api, output_api, white_list=None, black_list=None):
       return [output_api.PresubmitError(
           'Please install pylint with "sudo apt-get install python-setuptools; '
           'sudo easy_install pylint"\n'
+          'or visit http://pypi.python.org/pypi/setuptools.\n'
           'Cannot do static analysis of python files.')]
     if result:
       if input_api.is_committing:
diff --git a/presubmit_support.py b/presubmit_support.py
index 5a003eba00..fcc6a8555c 100755
--- a/presubmit_support.py
+++ b/presubmit_support.py
@@ -1,5 +1,5 @@
-#!/usr/bin/python
-# Copyright (c) 2010 The Chromium Authors. All rights reserved.
+#!/usr/bin/env python
+# Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
@@ -38,13 +38,8 @@ try:
   import simplejson as json  # pylint: disable=F0401
 except ImportError:
   try:
-    import json
-    # Some versions of python2.5 have an incomplete json module.  Check to make
-    # sure loads exists.
-    # Statement seems to have no effect
-    # pylint: disable=W0104
-    json.loads
-  except (ImportError, AttributeError):
+    import json  # pylint: disable=F0401
+  except ImportError:
     # Import the one included in depot_tools.
     sys.path.append(os.path.join(os.path.dirname(__file__), 'third_party'))
     import simplejson as json  # pylint: disable=F0401
diff --git a/trychange.py b/trychange.py
index a848c5b24c..003f040b26 100755
--- a/trychange.py
+++ b/trychange.py
@@ -1,5 +1,5 @@
-#!/usr/bin/python
-# Copyright (c) 2009 The Chromium Authors. All rights reserved.
+#!/usr/bin/env python
+# Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
@@ -25,20 +25,15 @@ try:
   import simplejson as json  # pylint: disable=F0401
 except ImportError:
   try:
-    import json
+    import json  # pylint: disable=F0401
   except ImportError:
-    json = None
+    # Import the one included in depot_tools.
+    sys.path.append(os.path.join(os.path.dirname(__file__), 'third_party'))
+    import simplejson as json  # pylint: disable=F0401
 
-try:
-  import breakpad  # pylint: disable=W0611
-except ImportError:
-  pass
-
-try:
-  import gcl
-except ImportError:
-  gcl = None
+import breakpad  # pylint: disable=W0611
 
+import gcl
 import fix_encoding
 import gclient_utils
 import scm
diff --git a/watchlists.py b/watchlists.py
index 57b810cb17..a6b5582aae 100755
--- a/watchlists.py
+++ b/watchlists.py
@@ -1,5 +1,5 @@
-#!/usr/bin/python
-# Copyright (c) 2009 The Chromium Authors. All rights reserved.
+#!/usr/bin/env python
+# Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.