Remove and replace encoding.string_types

Author: Harmon758

Diff for: gitdb/utils/encoding.py

@@ -1,18 +1,16 @@
 from gitdb.utils import compat
 
 if compat.PY3:
-    string_types = (str, )
     text_type = str
 else:
-    string_types = (basestring, )
     text_type = unicode
 
 
 def force_bytes(data, encoding="ascii"):
     if isinstance(data, bytes):
         return data
 
-    if isinstance(data, string_types):
+    if isinstance(data, str):
         return data.encode(encoding)
 
     return data