Merge pull request #257937 from RaitoBezarius/reduce-spam-for-boot

nixos/lib/test-driver: reduce spam at boot hangs

nixos/lib/test-driver/test_driver/machine.py

@@ -843,6 +843,9 @@ class Machine:
 
             while True:
                 chunk = self.shell.recv(1024)
+                # No need to print empty strings, it means we are waiting.
+                if len(chunk) == 0:
+                    continue
                 self.log(f"Guest shell says: {chunk!r}")
                 # NOTE: for this to work, nothing must be printed after this line!
                 if b"Spawning backdoor root shell..." in chunk: