Merge ~sylvain-pineau/checkbox-ng:more-remote-fixes into checkbox-ng:master

[Sylvain Pineau]

Two more patches for remote:

1. Ensure that the future services installed via snap install hooks will select the appropriate restart strategy (must be RemoteDebRestartStrategy)

2. XDG_SESSION_TYPE is added to the extra env var for jobs requiring a different command on wayland sessions.

[Maciej Kisielewski (kissiel)]

Looks good, totally landable. The shell invocation to extract XDG_SESSION_TYPE using bash chain bothered me, so I proposed python version instead below

review: Approve

[Sylvain Pineau (sylvain-pineau)]

Excellent idea, I've reworked my patches accordingly

diff --git a/checkbox_ng/launcher/slave.py b/checkbox_ng/launcher/slave.py
index c7e79df..c184371 100644
--- a/checkbox_ng/launcher/slave.py
+++ b/checkbox_ng/launcher/slave.py
@@ -116,8 +116,9 @@ class RemoteSlave():
         SessionAssistantSlave.session_assistant = RemoteSessionAssistant(
             lambda s: [sys.argv[0] + 'service'])
         snap_data = os.getenv('SNAP_DATA')
+        snap_rev = os.getenv('SNAP_REVISION')
         remote_restart_strategy_debug = os.getenv('REMOTE_RESTART_DEBUG')
-        if snap_data or remote_restart_strategy_debug or ctx.args.resume:
+        if (snap_data and snap_rev) or ctx.args.resume:
             if remote_restart_strategy_debug:
                 strategy = RemoteSnappyRestartStrategy(debug=True)
             else:
diff --git a/plainbox/impl/session/remote_assistant.py b/plainbox/impl/session/remote_assistant.py
index 5763e49..e3c6c11 100644
--- a/plainbox/impl/session/remote_assistant.py
+++ b/plainbox/impl/session/remote_assistant.py
@@ -27,7 +27,6 @@ from collections import namedtuple
 from contextlib import suppress
 from tempfile import SpooledTemporaryFile
 from threading import Thread, Lock
-from subprocess import CalledProcessError, check_output
 
 from plainbox.impl.execution import UnifiedRunner
 from plainbox.impl.session.assistant import SessionAssistant
@@ -211,26 +210,26 @@ class RemoteSessionAssistant():
         self._last_response = response
         self._state = Running
 
+    def _set_envvar_from_proc(self, name):
+        for path in os.listdir('/proc/'):
+            with suppress(Exception):
+                env = open(
+                    os.path.join('/proc/', path, 'environ')).read().split('\0')
+                for key, val in [item.split('=') for item in env]:
+                    if key == name:
+                        return val
+        return ''
+
     def _prepare_display_without_psutil(self):
-        try:
-            display_value = check_output(
-                'strings /proc/*/environ 2>/dev/null | '
-                'grep -m 1 -oP "(?<=DISPLAY=).*"',
-                shell=True, universal_newlines=True).rstrip()
-            xauth_value = check_output(
-                'strings /proc/*/environ 2>/dev/null | '
-                'grep -m 1 -oP "(?<=XAUTHORITY=).*"',
-                shell=True, universal_newlines=True).rstrip()
-            uid = pwd.getpwnam(self._normal_user).pw_uid
-            return {
-                'DISPLAY': display_value,
-                'XAUTHORITY': xauth_value,
-                'XDG_RUNTIME_DIR': '/run/user/{}'.format(uid),
-                'DBUS_SESSION_BUS_ADDRESS':
-                    'unix:path=/run/user/{}/bus'.format(uid)
-            }
-        except CalledProcessError:
-            return {}
+        uid = pwd.getpwnam(self._normal_user).pw_uid
+        return {
+            'DISPLAY': self._set_envvar_from_proc('DISPLAY'),
+            'XAUTHORITY': self._set_envvar_from_proc('XAUTHORITY'),
+            'XDG_SESSION_TYPE': self._set_envvar_from_proc('XDG_SESSION_TYPE'),
+            'XDG_RUNTIME_DIR': '/run/user/{}'.format(uid),
+            'DBUS_SESSION_BUS_ADDRESS':
+                'unix:path=/run/user/{}/bus'.format(uid)
+        }
 
     def prepare_extra_env(self):
         # If possible also set the DISPLAY env var
@@ -257,6 +256,7 @@ class RemoteSessionAssistant():
                 return {
                     'DISPLAY': p_environ['DISPLAY'],
                     'XAUTHORITY': p_environ['XAUTHORITY'],
+                    'XDG_SESSION_TYPE': p_environ['XDG_SESSION_TYPE'],
                     'XDG_RUNTIME_DIR': '/run/user/{}'.format(uid),
                     'DBUS_SESSION_BUS_ADDRESS':
                         'unix:path=/run/user/{}/bus'.format(uid)