Run pychecker over most scripts in depot_tools. Catched a few bugs.

presubmit_canned_checks.py

Index: presubmit_canned_checks.py
diff --git a/presubmit_canned_checks.py b/presubmit_canned_checks.py
index e67b9e18a75fc99c601bc3992310f85121119200..f9088d7831bcd12aacd2d1233aa1320e0c32d705 100755
--- a/presubmit_canned_checks.py
+++ b/presubmit_canned_checks.py
@@ -262,11 +262,11 @@ def CheckSvnProperty(input_api, output_api, prop, expected, affected_files):
   bad = filter(lambda f: f.Property(prop) != expected, affected_files)
   if bad:
     if input_api.is_committing:
-      type = output_api.PresubmitError
+      res_type = output_api.PresubmitError
     else:
-      type = output_api.PresubmitNotifyResult
+      res_type = output_api.PresubmitNotifyResult
     message = "Run `svn pset %s %s <item>` on these files:" % (prop, expected)
-    return [type(message, items=bad)]
+    return [res_type(message, items=bad)]
   return []