agentwrapper: try labgrid-python3 for agent environment

Allow probing of a labgrid-python3 executable and use that if available.
This allows the setup of a distinct python environment with the
necessary modules for agent operation. Since this is probed
automatically raise a debug message in case labgrid-python3 is not found
to aid in debugging.

Signed-off-by: Rouven Czerwinski <rouven.czerwinski@linaro.org>

Author: Emantor

labgrid/util/agentwrapper.py

@@ -4,6 +4,7 @@
 import os.path
 import socket
 import subprocess
+import shutil
 import traceback
 import logging
 
@@ -60,20 +61,31 @@ def __init__(self, host=None):
                 ['rsync', '-e', ' '.join(ssh_opts), '-tq', agent,
                  f'{host}:{agent_remote}'],
             )
+            agent_python = "labgrid-python3" if not subprocess.call(ssh_opts + [host, '--', 'which', 'labgrid-python3']) else "python3"
+            if agent_python == "python3":
+                self.logger.debug(
+                    "labgrid-python3 on %s not found, using python3 which requires system installed python modules for agents",
+                    host
+                )
             self.agent = subprocess.Popen(
-                ssh_opts + [host, '--', 'python3', agent_remote],
+                ssh_opts + [host, '--', agent_python, agent_remote],
                 stdin=subprocess.PIPE,
                 stdout=subprocess.PIPE,
                 start_new_session=True,
             )
         else:
             # run locally
             self.fdpass, remote_fdpass = socket.socketpair()
+            agent_python = "labgrid-python3" if shutil.which("labgrid-python3") else "python3"
+            if agent_python == "python3":
+                self.logger.debug(
+                    "labgrid-python3 not found locally, using python3 which requires system installed python modules for agents"
+                )
             with remote_fdpass:
                 env = os.environ.copy()
                 env["LG_FDPASS"] = str(remote_fdpass.fileno())
                 self.agent = subprocess.Popen(
-                    ['python3', agent],
+                    [agent_python, agent],
                     stdin=subprocess.PIPE,
                     stdout=subprocess.PIPE,
                     env=env,

tests/test_agent.py

@@ -1,6 +1,7 @@
 import os
 import socket
 import subprocess
+import shutil
 
 import pytest
 from py.path import local
@@ -18,7 +19,7 @@ def subprocess_mock(mocker):
     agent = local(labgrid.util.agentwrapper.__file__).dirpath('agent.py')
 
     def run(args, **kwargs):
-        assert args[0] in ['rsync', 'ssh']
+        assert args[0] in ['rsync', 'ssh', 'which']
         if args[0] == 'rsync':
             src = local(args[-2])
             assert src == agent
@@ -32,10 +33,14 @@ def run(args, **kwargs):
             assert '--' in args
             args = args[args.index('--')+1:]
             assert len(args) == 2
-            assert args[0] == 'python3'
-            assert args[1].startswith('.labgrid_agent')
-            # we need to use the original here to get the coverage right
-            return original(['python3', str(agent)], **kwargs)
+            assert args[0] in ['labgrid-python3', 'python3', 'which']
+            if args[0] in ['python3', 'labgrid-python3']:
+                assert args[1].startswith('.labgrid_agent')
+                # we need to use the original here to get the coverage right
+                return original(['python3', str(agent)], **kwargs)
+            else:
+                lg_py3_env = 'true' if shutil.which('labgrid-python3') else 'false'
+                return original([lg_py3_env], **kwargs)
 
     mocker.patch('subprocess.Popen', run)