Add a osutils module for simple file/os manipulation ops.

Basically removes some boilerplate, while making a few trickier
things (atomic file updates for example) accessible via a clean
api.

BUG=None
TEST=run_tests
TEST=cbuildbot x86-generic-paladin --remote
TEST=cbuildbot x86-generic-paladin --buildbot <usual>

Change-Id: I22cd73ffc4480974dbd0a2e154c7a364405e2b8e
Reviewed-on: https://gerrit.chromium.org/gerrit/22415
Commit-Ready: Brian Harring <ferringb@chromium.org>
Reviewed-by: Brian Harring <ferringb@chromium.org>
Tested-by: Brian Harring <ferringb@chromium.org>
diff --git a/scripts/cbuildbot.py b/scripts/cbuildbot.py
index 107f15f..17e35c1 100644
--- a/scripts/cbuildbot.py
+++ b/scripts/cbuildbot.py
@@ -35,6 +35,7 @@
 from chromite.lib import cgroups
 from chromite.lib import cleanup
 from chromite.lib import cros_build_lib as cros_lib
+from chromite.lib import osutils
 from chromite.lib import sudo
 
 
@@ -568,7 +569,7 @@
     dirname = options.log_dir or default_dir
     log_file = os.path.join(dirname, _BUILDBOT_LOG_FILE)
 
-    cros_lib.SafeMakedirs(dirname)
+    osutils.SafeMakedirs(dirname)
     _BackupPreviousLog(log_file)
 
   try: