Unify calling the editor in EditCommand

Now every call to editor is done by `EditCommand._open_in_editor()` and
whole process of getting editor name is also done there.

test/EditCommandTest.py

@@ -139,7 +139,7 @@ class EditCommandTest(CommandTest):
         self.assertEqual(self.output, expected)
         self.assertEqual(self.todolist.print_todos(), u("Foo id:1\nFo\u00f3B\u0105\u017a\nLazy Cat\nLazy Dog"))
 
-    @mock.patch('topydo.commands.EditCommand.call')
+    @mock.patch('topydo.commands.EditCommand.check_call')
     def test_edit_archive(self, mock_call):
         """ Edit archive file. """
         mock_call.return_value = 0

topydo/commands/EditCommand.py

@@ -73,12 +73,20 @@ class EditCommand(MultiCommand, ExpressionCommand):
 
         return todo_objs
 
-    def _open_in_editor(self, p_temp_file, p_editor):
+    def _open_in_editor(self, p_file):
         try:
-            return check_call([p_editor, p_temp_file.name])
+            editor = os.environ['EDITOR'] or DEFAULT_EDITOR
+        except(KeyError):
+            editor = DEFAULT_EDITOR
+
+        try:
+            return check_call([editor, p_file])
         except CalledProcessError:
             self.error('Something went wrong in the editor...')
             return 1
+        except(OSError):
+            self.error('There is no such editor as: ' + editor + '. '
+                        'Check your $EDITOR and/or $PATH')
 
     def _catch_todo_errors(self):
         errors = []
@@ -99,23 +107,18 @@ class EditCommand(MultiCommand, ExpressionCommand):
             return False
 
         self.printer.add_filter(PrettyPrinterNumbers(self.todolist))
-        try:
-            editor = os.environ['EDITOR'] or DEFAULT_EDITOR
-        except(KeyError):
-            editor = DEFAULT_EDITOR
 
-        try:
         if len(self.args) < 1:
             todo = config().todotxt()
 
-                return call([editor, todo]) == 0
+            return self._open_in_editor(todo) == 0
         else:
             self._process_flags()
 
             if self.edit_archive:
                 archive = config().archive()
 
-                    return call([editor, archive]) == 0
+                return self._open_in_editor(archive) == 0
 
             if self.is_expression:
                 self.todos = self._view().todos
@@ -127,7 +130,7 @@ class EditCommand(MultiCommand, ExpressionCommand):
             if not todo_errors:
                 temp_todos = self._todos_to_temp()
 
-                    if not self._open_in_editor(temp_todos, editor):
+                if not self._open_in_editor(temp_todos):
                     new_todos = self._todos_from_temp(temp_todos)
                     if len(new_todos) == len(self.todos):
                         for todo in self.todos:
@@ -144,9 +147,6 @@ class EditCommand(MultiCommand, ExpressionCommand):
             else:
                 for error in todo_errors:
                     self.error(error)
-        except(OSError):
-            self.error('There is no such editor as: ' + editor + '. '
-                        'Check your $EDITOR and/or $PATH')
 
     def usage(self):
         return """Synopsis: