nixosTests: Drop invalid utf characters in command output

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

@@ -395,7 +395,7 @@ class Machine:
         status_code_pattern = re.compile(r"(.*)\|\!EOF\s+(\d+)")
 
         while True:
-            chunk = self.shell.recv(4096).decode()
+            chunk = self.shell.recv(4096).decode(errors="ignore")
             match = status_code_pattern.match(chunk)
             if match:
                 output += match[1]