Removed polyglots unicode_type usage

ebook_converter/utils/short_uuid.py

@@ -3,8 +3,6 @@ Generate UUID encoded using a user specified alphabet.
 '''
 import string, math, uuid as _uuid
 
-from ebook_converter.polyglot.builtins import unicode_type
-
 
 def num_to_string(number, alphabet, alphabet_len, pad_to_length=None):
     ans = []
@@ -30,7 +28,7 @@ class ShortUUID(object):
         # We do not include zero and one in the default alphabet as they can be
         # confused with the letters O and I in some fonts. And removing them
         # does not change the uuid_pad_len.
-        self.alphabet = tuple(sorted(unicode_type(alphabet or (string.digits + string.ascii_letters)[2:])))
+        self.alphabet = tuple(sorted(str(alphabet or (string.digits + string.ascii_letters)[2:])))
         self.alphabet_len = len(self.alphabet)
         self.alphabet_map = {c:i for i, c in enumerate(self.alphabet)}
         self.uuid_pad_len = int(math.ceil(math.log(1 << 128, self.alphabet_len)))