Port os.rename calls to work on Windows

os.rename fails on Windows if the destination exists, so replace
os.rename to platform_utils.rename which handles the platform
differences.

Change-Id: I15a86f10f65eedee5b003b80f88a0c28a3e1aa48

platform_utils.py

@@ -13,6 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import errno
 import os
 import platform
 import select
@@ -225,3 +226,19 @@ def handle_rmtree_error(function, path, excinfo):
   # Allow deleting read-only files
   os.chmod(path, stat.S_IWRITE)
   function(path)
+
+
+def rename(src, dst):
+  if isWindows():
+    # On Windows, rename fails if destination exists, see
+    # https://docs.python.org/2/library/os.html#os.rename
+    try:
+      os.rename(src, dst)
+    except OSError as e:
+      if e.errno == errno.EEXIST:
+        os.remove(dst)
+        os.rename(src, dst)
+      else:
+        raise
+  else:
+    os.rename(src, dst)

project.py

@@ -63,7 +63,7 @@ def _lwrite(path, content):
     fd.close()
 
   try:
-    os.rename(lock, path)
+    platform_utils.rename(lock, path)
   except OSError:
     os.remove(lock)
     raise
@@ -2198,7 +2198,7 @@ class Project(object):
 
     if os.path.exists(tmpPath):
       if curlret == 0 and self._IsValidBundle(tmpPath, quiet):
-        os.rename(tmpPath, dstPath)
+        platform_utils.rename(tmpPath, dstPath)
         return True
       else:
         os.remove(tmpPath)