Port beets.logging to python 2.6

Multiple hacks :-)

beets/logging.py

@@ -2,11 +2,15 @@
 
 Provide everything the "logging" module does, the only difference is that when
 getLogger(name) instantiates a logger that logger uses {}-style formatting.
+
+It requires special hacks for python 2.6 due to logging.Logger being an old-
+style class and having no loggerClass attribute.
 """
 
 from __future__ import absolute_import
 from copy import copy
 from logging import *  # noqa
+import sys
 
 
 # create a str.format-based logger
@@ -23,8 +27,21 @@ class StrFormatLogger(Logger):
     def _log(self, level, msg, args, exc_info=None, extra=None, **kwargs):
         """Log msg.format(*args, **kwargs)"""
         m = self._LogMessage(msg, args, kwargs)
-        return super(StrFormatLogger, self)._log(level, m, (), exc_info, extra)
+        return Logger._log(self, level, m, (), exc_info, extra)
+        # we cannot call super(StrFormatLogger, self) because it is not
+        # allowed on old-style classes (py2) which Logger is in python 2.6
+        # moreover we cannot make StrFormatLogger a new-style class (by
+        # declaring 'class StrFormatLogger(Logger, object)' because the class-
+        # patching stmt 'logger.__class__ = StrFormatLogger' would not work:
+        # both prev & new __class__ values must be either old- or new- style,
+        # no mixing allowed.
 
+    if sys.version_info[:2] == (2, 6):
+        def getChild(self, suffix):
+            """Shameless copy from cpython's Lib/logging/__init__.py"""
+            if self.root is not self:
+                suffix = '.'.join((self.name, suffix))
+            return self.manager.getLogger(suffix)
 
 my_manager = copy(Logger.manager)
 my_manager.loggerClass = StrFormatLogger
@@ -35,3 +52,21 @@ def getLogger(name=None):
         return my_manager.getLogger(name)
     else:
         return root
+
+
+if sys.version_info[:2] == (2, 6):
+    # no Manager.loggerClass so we dynamically change the logger class
+    # we must be careful to do that on new loggers only to avoid side-effects.
+    # Wrap Manager.getLogger
+    old_getLogger = my_manager.getLogger
+
+    def new_getLogger(name):
+        change_its_type = not isinstance(my_manager.loggerDict.get(name),
+                                         Logger)
+        # it either does not exist or is a placeholder
+        logger = old_getLogger(name)
+        if change_its_type:
+            logger.__class__ = StrFormatLogger
+        return logger
+
+    my_manager.getLogger = new_getLogger

test/test_logging.py

@@ -11,15 +11,15 @@ class LoggingTest(TestCase):
         l1 = log.getLogger("foo123")
         l2 = blog.getLogger("foo123")
         self.assertEqual(l1, l2)
-        self.assertEqual(type(l1), log.Logger)
+        self.assertEqual(l1.__class__, log.Logger)
 
         l3 = blog.getLogger("bar123")
         l4 = log.getLogger("bar123")
         self.assertEqual(l3, l4)
-        self.assertEqual(type(l3), blog.StrFormatLogger)
+        self.assertEqual(l3.__class__, blog.StrFormatLogger)
 
         l5 = l3.getChild("shalala")
-        self.assertEqual(type(l5), blog.StrFormatLogger)
+        self.assertEqual(l5.__class__, blog.StrFormatLogger)
 
     def test_str_format_logging(self):
         l = blog.getLogger("baz123")
@@ -29,7 +29,7 @@ class LoggingTest(TestCase):
         l.addHandler(handler)
         l.propagate = False
 
-        l.warning("foo {} {bar}", "oof", bar="baz")
+        l.warning("foo {0} {bar}", "oof", bar="baz")
         handler.flush()
         self.assertTrue(stream.getvalue(), "foo oof baz")