Fix PyChecker errors caused by r26423.

Patch contributed by msb@

TEST=unit test
BUG=none

Review url: http://codereview.chromium.org/213006


git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@26457 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/gclient_utils.py b/gclient_utils.py
index 1b11f96..464419f 100644
--- a/gclient_utils.py
+++ b/gclient_utils.py
@@ -12,11 +12,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import errno
 import os
 import stat
 import subprocess
 import sys
+import time
 import xml.dom.minidom
+import xml.parsers.expat
 
 ## Generic utils