target/ast10x0/harness: surface SSH errors immediately during lock acquisition

target/ast10x0/harness/test_runner.py

diff --git a/target/ast10x0/harness/test_runner.py b/target/ast10x0/harness/test_runner.py
index 7577c9f..a49188d 100644
--- a/target/ast10x0/harness/test_runner.py
+++ b/target/ast10x0/harness/test_runner.py
@@ -105,9 +105,14 @@
         r = _ssh(host, create, capture_output=True)
         if r.returncode == 0:
             return True
+        if r.stderr.strip():
+            print(r.stderr.decode(errors="replace").strip(), file=sys.stderr)
+            return False
         _ssh(host, stale_check, capture_output=True)
         time.sleep(2)
-    print(f"Timeout acquiring Pi lock after {timeout}s", file=sys.stderr)
+    print(
+        f"Timeout acquiring Pi lock after {timeout}s (Pi may be busy)", file=sys.stderr
+    )
     return False