Initial python3 changes

Mostly just updating libraries, removing string encoding/decoding,
fixing some edge cases. No new functionality was added in this
commit.

lib/beetsplug/fuzzy.py

@@ -0,0 +1,46 @@
+# This file is part of beets.
+# Copyright 2016, Philippe Mongeau.
+#
+# Permission is hereby granted, free of charge, to any person obtaining
+# a copy of this software and associated documentation files (the
+# "Software"), to deal in the Software without restriction, including
+# without limitation the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the Software, and to
+# permit persons to whom the Software is furnished to do so, subject to
+# the following conditions:
+#
+# The above copyright notice and this permission notice shall be
+# included in all copies or substantial portions of the Software.
+
+"""Provides a fuzzy matching query.
+"""
+
+
+from beets.plugins import BeetsPlugin
+from beets.dbcore.query import StringFieldQuery
+from beets import config
+import difflib
+
+
+class FuzzyQuery(StringFieldQuery):
+    @classmethod
+    def string_match(cls, pattern, val):
+        # smartcase
+        if pattern.islower():
+            val = val.lower()
+        query_matcher = difflib.SequenceMatcher(None, pattern, val)
+        threshold = config['fuzzy']['threshold'].as_number()
+        return query_matcher.quick_ratio() >= threshold
+
+
+class FuzzyPlugin(BeetsPlugin):
+    def __init__(self):
+        super().__init__()
+        self.config.add({
+            'prefix': '~',
+            'threshold': 0.7,
+        })
+
+    def queries(self):
+        prefix = self.config['prefix'].as_str()
+        return {prefix: FuzzyQuery}