Fix presubmit_unittests on some versions of python2.5.

On our hardy boxes, the python has the json module, but it doesn't
have all the expected methods.  Fallback to simplejson if it
doesn't have json.loads().

Review URL: http://codereview.chromium.org/1520025

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@43907 0039d316-1c4b-4281-b951-d872f2087c98

presubmit_support.py

@@ -39,7 +39,10 @@ try:
 except ImportError:
   try:
     import json
-  except ImportError:
+    # Some versions of python2.5 have an incomplete json module.  Check to make
+    # sure loads exists.
+    json.loads
+  except (ImportError, AttributeError):
     # Import the one included in depot_tools.
     sys.path.append(os.path.join(os.path.dirname(__file__), 'third_party'))
     import simplejson as json