Pass along RunCommandException correctly. This is a minor

fix, but it leads to better error messages from ctest.

Change-Id: I624ad805ef037b022e6e67b56f0ed10ca05fe325

BUG=11096
TEST=Test currently in progress.

Review URL: http://codereview.chromium.org/6257007

lib/cros_build_lib.py

@@ -81,9 +81,9 @@ def RunCommand(cmd, print_cmd=True, error_ok=False, error_message=None,
 
       raise RunCommandException('Command "%r" failed.\n' % (cmd) +
                                 (error_message or error or output or ''))
-    except Exception, e:
+    except RunCommandException as e:
       if not error_ok and retry_count == num_retries:
-        raise RunCommandException(e)
+        raise e
       else:
         Warning(str(e))
         if print_cmd: