Launchd 启动失败：“由于某些奇怪原因，无法执行（3）”

Question

我设置了一个非常简单的 lanuchd 任务来在每天的特定时间启动备份脚本。

我可以从命令行完美地运行该命令而没有任何问题，但是当尝试通过 lauchd 启动时，会出现以下系统日志错误

9/4/14 9:30:17.534 AM com.apple.launchd.peruser.503[422]: (local.meviocorp.BSbackupScripts[1938]) Job failed to exec(3). Setting up event to tell us when to try again: 2: No such file or directory
9/4/14 9:30:17.534 AM com.apple.launchd.peruser.503[422]: (local.meviocorp.BSbackupScripts[1938]) Job failed to exec(3) for weird reason: 2
9/4/14 9:30:17.535 AM com.apple.launchd.peruser.503[422]: (local.meviocorp.BSbackupScripts) Job should be able to exec(3) now.

plist 非常简单，我无法想象这就是问题所在：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>Label</key>
    <string>local.meviocorp.BSbackupScripts</string>
    <key>ProgramArguments</key>
    <array>
        <string>bs_production_backup.py</string>
        <string></string>
    </array>
    <key>StartCalendarInterval</key>
    <dict>
        <key>Hour</key>
        <integer>9</integer>
        <key>Minute</key>
        <integer>30</integer>
    </dict>
</dict>
</plist>

有什么想法下一步该去哪里吗？