Run system sumo with snap Webots (cyberbotics#6253)

* Adjust SumoInterface to run externController

* Update sumo-interface.md

* Update sumo-interface.md

* Update projects/default/controllers/sumo_supervisor/sumo_supervisor.py

Co-authored-by: Olivier Michel <Olivier.Michel@cyberbotics.com>

---------

Co-authored-by: Olivier Michel <Olivier.Michel@cyberbotics.com>

Author: stefaniapedrazzi

docs/automobile/sumo-interface.md

@@ -21,6 +21,15 @@ sudo apt install sumo sumo-tools sumo-doc
 
 `SUMO_HOME` environment variable will be automatically set during the installation, but it may be necessary to logout and login, or even reboot, after the installation to correctly run the SUMO Interface.
 
+<br />
+
+Note that if you installed Webots using the snap package, Webots will be unable to launch the SUMO because of the snap sand-boxing.
+To work around this problem, the `SumoInterface.exterController` field should be set to TRUE and the controller should be launched as [extern controller](../guide/running-extern-robot-controllers.md) from outside Webots by running these commands:
+```sh
+export WEBOTS_HOME=/snap/webots/current/usr/share/webots
+$WEBOTS_HOME/webots-controller $WEBOTS_HOME/projects/default/controllers/sumo_supervisor/sumo_supervisor.py
+```
+
 #### macOS
 
 Using [Homebrew](https://brew.sh), first install [XQuartz](https://www.xquartz.org) for the SUMO interface, that relies on X11, to work:

docs/guide/installation-procedure.md

@@ -145,7 +145,7 @@ However, when developing robot controllers, it is often useful to use various co
 If such components are needed, users can install them on their system or local environment to create, possibly compile and link their robot controllers.
 However, because of the snap sand-boxing, Webots will be unable to launch these controller itself.
 To work around this problem, such controllers should be launched as extern controllers from outside of Webots.
-Before launching extern controllers, you should set the `WEBOTS_HOME` environment variable to point to `/snap/webots/current/usr/share/webots` and add `$WEBOTS_HOME/lib/controller` to your `LD_LIBRARY_PATH` environment variable, so that your controllers will find the necessary shared libraries.
+Before launching extern controllers, you should set the `WEBOTS_HOME` environment variable to point to `/snap/webots/current/usr/share/webots` and run the `$WEBOTS_HOME/webots-controller` launcher.
 The chapter entitled [running extern robot controllers](running-extern-robot-controllers.md) details how to run extern controllers, including with the snap version of Webots.
 
 #### Installing the Docker Image

projects/default/controllers/sumo_supervisor/sumo_supervisor.py

@@ -28,10 +28,15 @@
 def sumoImportError():
     sys.stderr.write("SUMO not found.\n")
     if sys.platform.startswith('linux'):
-        sys.stderr.write("Please install it with `sudo apt install sumo sumo-tools` and reboot.\n")
+        if os.getenv('SNAP_NAME'):
+            sys.stderr.write("Please set the 'SumoInterface.externController' field to TRUE and "
+                             "launch the controller as extern controller.\n"
+                             "Install SUMO ")
+        else:
+            sys.stderr.write("Please install it ")
+        sys.stderr.write("with `sudo apt install sumo sumo-tools` and reboot.\n")
     else:
         sys.stderr.write("Please install it following the instructions at https://sumo.dlr.de/docs/Installing/.\n")
-        pass
     sys.exit("Or check that the SUMO_HOME environment variable points to the directory of your SUMO installation.")
 
 

projects/default/protos/SumoInterface.proto

@@ -25,6 +25,7 @@ PROTO SumoInterface [
   field SFNode    display               NULL
   field SFBool    verbose               FALSE
   field SFBool    synchronization       TRUE
+  field SFBool    externController      FALSE
   field MFNode    children              []
   hiddenField SFBool  enableWheelsRoattion  FALSE  # deprecated in Webots 2018a.
   hiddenField SFInt32 maxVehicules          100    # deprecated in Webots 2018a.
@@ -86,7 +87,11 @@ PROTO SumoInterface [
   Robot {
     name IS name
     model "SUMO interface"
+    %< if (fields.externController.value) { >%
+    controller "<extern>"
+    %< } else { >%
     controller "sumo_supervisor"
+    %< } >%
     controllerArgs [
       %< for (let i = 0; i < controllerArguments.length; ++i) { >%
       %<= '"' + controllerArguments[i] + '"\n' >%