Unfortunately the module doesn't support strings & bytes simultaneously,
it's only selected at build time by this constant.  The only usage of this
module we have in CrOS is for bytes, so disable string support when building
for Python 3 (since the Python 2 code only supports bytes).  If people want
to compare strings, they can convert to bytes first, but it's impossible to
convert all binary data into strings for comparing.

https://github.com/WojciechMula/pyahocorasick/issues/65

--- a/setup.py
+++ b/setup.py
@@ -33,7 +33,6 @@
 if python_version.major == 3:
     macros = [
         # when defined unicode strings are supported
-        ('AHOCORASICK_UNICODE', ''),
     ]
 else:
     # On Python 2, unicode strings are not supported (yet).