PY3: switch to using unicode text values

In Python 3, python-ldap no longer allows bytes for DN/RDN/field
names. Instead, text values are represented as str, the Unicode
text type.

This patch updates the code to adhere to this behavior.

More details about byte/str usage in python-ldap can be found at:
http://www.python-ldap.org/en/latest/bytes_mode.html#bytes-mode

Change-Id: I9ef10432229aaffe4ac9bd733d608098cdae3b9a
Partial-Bug: #1798184

ldappool/__init__.py

@@ -44,6 +44,7 @@ import time
 import ldap
 from ldap.ldapobject import ReconnectLDAPObject
 import six
+from six import PY2
 
 log = logging.getLogger(__name__)
 _utf8_encoder = codecs.getencoder('utf-8')
@@ -167,7 +168,8 @@ class ConnectionManager(object):
 
     def _match(self, bind, passwd):
         if passwd is not None:
-            passwd = utf8_encode(passwd)
+            if PY2:
+                passwd = utf8_encode(passwd)
         with self._pool_lock:
             inactives = []
 
@@ -240,7 +242,8 @@ class ConnectionManager(object):
         tries = 0
         connected = False
         if passwd is not None:
-            passwd = utf8_encode(passwd)
+            if PY2:
+                passwd = utf8_encode(passwd)
         exc = None
         conn = None