Clean activity logs successful completion

Status zero is normal, so don't report it.

Also don't print the log_file object.

Changes log messages such as this;

Exited with status 0, pid 3765 data (<_io.TextIOWrapper name=13 mode='w'
encoding='UTF-8'>, '5312a7726254b3b0b9a15267c54600aec9db187e')

To this;

Normal successful completion, pid 3765 activity_id 5312a7726254b3b0b9a15267c54600aec9db187e

src/sugar3/activity/activityfactory.py

@@ -301,7 +301,10 @@ def _child_watch_cb(pid, condition, user_data):
     if os.WIFEXITED(condition):
         status = os.WEXITSTATUS(condition)
         signum = None
-        message = 'Exited with status %s' % status
+        if status == 0:
+            message = 'Normal successful completion'
+        else:
+            message = 'Exited with status %s' % status
     elif os.WIFSIGNALED(condition):
         status = None
         signum = os.WTERMSIG(condition)
@@ -312,7 +315,8 @@ def _child_watch_cb(pid, condition, user_data):
         message = 'Undefined status with signal %s' % signum
 
     try:
-        log_file.write('%s, pid %s data %s\n' % (message, pid, user_data))
+        log_file.write(
+            '%s, pid %s activity_id %s\n' % (message, pid, activity_id))
     finally:
         log_file.close()