Fix mixup stdout/stderr

Author: spoorcc

dfetch/util/cmdline.py

@@ -25,8 +25,8 @@ def __init__(
         cmd_str: str = " ".join(cmd or [])
         self._message = f">>>{cmd_str}<<< returned {returncode}:{os.linesep}{stderr}"
         self.cmd = cmd_str
-        self.stderr = stdout
-        self.stdout = stderr
+        self.stderr = stderr
+        self.stdout = stdout
         self.returncode = returncode
         super().__init__(self._message)