sshdriver: Log keepalive output

While it is not normally expected for the keepalive process to produce
any output, it can be helpful for debugging purposes to log any output
it may have produced. As such, try harder to get output when terminating
the process, and also report any output after it exits

Signed-off-by: Joshua Watt <[email protected]>

labgrid/driver/sshdriver.py

@@ -527,7 +527,8 @@ def _start_keepalive(self):
             args,
             stdin=subprocess.PIPE,
             stdout=subprocess.PIPE,
-            stderr=subprocess.PIPE,
+            stderr=subprocess.STDOUT,
+            encoding="utf-8",
         )
 
         self.logger.debug('Started keepalive for %s', self.networkservice.address)
@@ -540,12 +541,19 @@ def _stop_keepalive(self):
 
         self.logger.debug('Stopping keepalive for %s', self.networkservice.address)
 
+        stdout = None
         try:
-            self._keepalive.communicate(timeout=60)
+            stdout, _ = self._keepalive.communicate(timeout=60)
         except subprocess.TimeoutExpired:
             self._keepalive.kill()
-
-        try:
-            self._keepalive.wait(timeout=60)
+            try:
+                # Try again to get output
+                stdout, _ = self._keepalive.communicate(timeout=60)
+            except subprocess.TimeoutExpired:
+                self.logger.warning("ssh keepalive for %s timed out during termination", self.networkservice.address)
         finally:
             self._keepalive = None
+
+        if stdout:
+            for line in stdout.splitlines():
+                self.logger.warning("Keepalive %s: %s", self.networkservice.address, line)