http://kerpau.net/robocopy-exit-codes/
Hex Bit Value Decimal Value Meaning If Set
0×10 16 Serious error. Robocopy did not copy any files. This is either a usage error or an error due to insufficient access privileges on the source or destination directories.
0×08 8 Some files or directories could not be copied (copy errors occurred and the retry limit was exceeded). Check these errors further.
0×04 4 Some Mismatched files or directories were detected. Examine the output log. Housekeeping is probably necessary.
0×02 2 Some Extra files or directories were detected. Examine the output log. Some housekeeping may be needed.
0×01 1 One or more files were copied successfully (that is, new files have arrived).
0×00 0 No errors occurred, and no copying was done. The source and destination directory trees are completely synchronized.
正直0x01, 0x02を返してほしくない・・・
Visual Studio が失敗と判断するでしょ！！