Try language_level=3 (#329)

methane · web-flow · commit 2f808b6e012b · 2018-11-14T20:04:22.000+09:00
diff --git a/msgpack/_cmsgpack.pyx b/msgpack/_cmsgpack.pyx
@@ -1,4 +1,4 @@
 # coding: utf-8
-#cython: embedsignature=True, c_string_encoding=ascii, language_level=2
+#cython: embedsignature=True, c_string_encoding=ascii, language_level=3
 include "_packer.pyx"
 include "_unpacker.pyx"
