backends: Ensure export command is called in the form 'task <filter> export'

This is required for Taskwarrior 2.6.0+ compatibility.

Author: tbabej

tasklib/backends.py

@@ -329,7 +329,7 @@ def get_task(self, uuid):
 
     def filter_tasks(self, filter_obj):
         self.enforce_recurrence()
-        args = ['export'] + filter_obj.get_filter_params()
+        args = filter_obj.get_filter_params() + ["export"]
         tasks = []
         for line in self.execute_command(args):
             if line:
@@ -427,8 +427,7 @@ def valid(output):
             for key, value in data.items():
                 taskfilter.add_filter_param(key, value)
 
-            output = self.execute_command(['export'] +
-                                          taskfilter.get_filter_params())
+            output = self.execute_command(taskfilter.get_filter_params() + ['export'])
 
         # If more than 1 task has been matched still, raise an exception
         if not valid(output):