Fix import of simplejson included in depot_tools

TEST=verified it works in python 2.4
BUG=none

Review URL: http://codereview.chromium.org/1110006

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@42177 0039d316-1c4b-4281-b951-d872f2087c98

presubmit_support.py

@@ -41,7 +41,8 @@ except ImportError:
     import json
   except ImportError:
     # Import the one included in depot_tools.
-    import third_party.simplejson as json
+    sys.path.append(os.path.join(os.path.dirname(__file__), 'third_party'))
+    import simplejson as json
 
 # Local imports.
 import gcl