Python standard library is not thread safe. Work around it by leaking a bit.
The problem is particularly visible on python 2.4.

TEST=none
BUG=60623

Review URL: http://codereview.chromium.org/4465001

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@65048 0039d316-1c4b-4281-b951-d872f2087c98