ctl: only install dnf4 if it is missing

Tiny tweak, we only need to install dnf4 when its actually missing.
This is also the only piece in the code that requires root right
now (AFAICT) so dropping it has the extra benefit that we can run
as non-root again.

Author: mvo5

src/ctl/pull.py

@@ -9,6 +9,7 @@
 import contextlib
 import errno
 import os
+import shutil
 import subprocess
 import sys
 import tempfile
@@ -71,7 +72,8 @@ def __exit__(self, exc_type, exc_value, exc_tb):
         self._exitstack = None
 
     def _run_reposync(self):
-        subprocess.run(["dnf", "install", "-y", "dnf4"], stdout=subprocess.PIPE, check=True)
+        if not shutil.which("dnf4"):
+            subprocess.run(["dnf", "install", "-y", "dnf4"], stdout=subprocess.PIPE, check=True)
 
         cmd = [
             "dnf4", "reposync",