Remove unused imports (PyMySQL#835)

Author: vilhelmprytz

pymysql/_auth.py

@@ -1,8 +1,7 @@
 """
 Implements auth methods
 """
-from ._compat import text_type, PY2
-from .constants import CLIENT
+from ._compat import PY2
 from .err import OperationalError
 from .util import byte2int, int2byte
 

pymysql/converters.py

@@ -5,8 +5,7 @@
 import re
 import time
 
-from .constants import FIELD_TYPE, FLAG
-from .charset import charset_by_id
+from .constants import FIELD_TYPE
 
 
 def escape_item(val, charset, mapping=None):