hglib: introduce util.b() (issue4520) The util.b() function will be used to mark all string literals in the code base which should be treated as bytes instead of text. This is to help with supporting Python 3.

import common
import hglib

class test_encoding(common.basetest):
    def test_basic(self):
        self.client = hglib.open(encoding='utf-8')
        self.assertEquals(self.client.encoding, 'utf-8')