exporter: Check /usr/sbin for ser2net

On Debian, the ser2net binary is installed at /usr/sbin/ser2net and it
can be run by any user. Since this isn't on the users PATH, we should
attempt to use it when failing to find a ser2net binary, before falling
back to /usr/bin/ser2net.

Signed-off-by: Thomas Preston <thomas.preston@codethink.co.uk>

Author: Thomas Preston

CHANGES.rst

@@ -17,6 +17,7 @@ New Features in 0.4.0
   make them easier distinguishable from pytest's "PASSED" output.
 - Network controlled relay providing GET/PUT based REST API
 - Improved LG_PROXY documentation in docs/usage.rst.
+- Exporter now checks /usr/sbin/ser2net for SerialPortExport
 
 Bug fixes in 0.4.0
 ~~~~~~~~~~~~~~~~~~

labgrid/remote/exporter.py

@@ -6,6 +6,7 @@
 import logging
 import sys
 import os
+import os.path
 import time
 import traceback
 import shutil
@@ -191,8 +192,12 @@ def __attrs_post_init__(self):
         self.port = None
         self.ser2net_bin = shutil.which("ser2net")
         if self.ser2net_bin is None:
-            warnings.warn("ser2net binary not found, falling back to /usr/bin/ser2net")
-            self.ser2net_bin = "/usr/bin/ser2net"
+            if os.path.isfile("/usr/sbin/ser2net"):
+                self.ser2net_bin = "/usr/sbin/ser2net"
+
+            if self.ser2net_bin is None:
+                warnings.warn("ser2net binary not found, falling back to /usr/bin/ser2net")
+                self.ser2net_bin = "/usr/bin/ser2net"
 
     def __del__(self):
         if self.child is not None: