convert: uses new par_map to work in parallel (#3830)

Squashed 5 commits:
* convert: uses new par_map to work in parallel
* linting
* code review: remove unneeded list syntax
* linting
* changelog addition

beetsplug/convert.py

@@ -16,6 +16,7 @@
 """Converts tracks or albums to external directory
 """
 from __future__ import division, absolute_import, print_function
+from beets.util import par_map
 
 import os
 import threading
@@ -183,8 +184,8 @@ class ConvertPlugin(BeetsPlugin):
 
     def auto_convert(self, config, task):
         if self.config['auto']:
-            for item in task.imported_items():
-                self.convert_on_import(config.lib, item)
+            par_map(lambda item: self.convert_on_import(config.lib, item),
+                    task.imported_items())
 
     # Utilities converted from functions to methods on logging overhaul
 

docs/changelog.rst

@@ -6,6 +6,7 @@ Changelog
 
 New features:
 
+* conversion uses par_map to parallelize conversion jobs in python3
 * Add ``title_case`` config option to lastgenre to make TitleCasing optional.
 * When config is printed with no available configuration a new message is printed.
   :bug:`3779`