Define unicode for Python 3

Author: cclauss

snappy/snappy_cffi.py

@@ -1,8 +1,15 @@
 from _snappy_cffi import ffi, lib
 
+try:
+    unicode        # Python 2
+except NameError:
+    unicode = str  # Python 3
+
+
 class UncompressError(Exception):
     pass
 
+
 class SnappyBufferSmallError(Exception):
     pass