Update beets to 1.4.7

Also updates:
- colorama-0.4.1
- jellyfish-0.6.1
- munkres-1.0.12
- musicbrainzngs-0.6
- mutagen-1.41.1
- pyyaml-3.13
- six-1.12.0
- unidecode-1.0.23

libs/yaml/error.py

@@ -1,7 +1,7 @@
 
 __all__ = ['Mark', 'YAMLError', 'MarkedYAMLError']
 
-class Mark(object):
+class Mark:
 
     def __init__(self, name, index, line, column, buffer, pointer):
         self.name = name
@@ -16,7 +16,7 @@ class Mark(object):
             return None
         head = ''
         start = self.pointer
-        while start > 0 and self.buffer[start-1] not in u'\0\r\n\x85\u2028\u2029':
+        while start > 0 and self.buffer[start-1] not in '\0\r\n\x85\u2028\u2029':
             start -= 1
             if self.pointer-start > max_length/2-1:
                 head = ' ... '
@@ -24,13 +24,13 @@ class Mark(object):
                 break
         tail = ''
         end = self.pointer
-        while end < len(self.buffer) and self.buffer[end] not in u'\0\r\n\x85\u2028\u2029':
+        while end < len(self.buffer) and self.buffer[end] not in '\0\r\n\x85\u2028\u2029':
             end += 1
             if end-self.pointer > max_length/2-1:
                 tail = ' ... '
                 end -= 5
                 break
-        snippet = self.buffer[start:end].encode('utf-8')
+        snippet = self.buffer[start:end]
         return ' '*indent + head + snippet + tail + '\n'  \
                 + ' '*(indent+self.pointer-start+len(head)) + '^'