setup.py

--- a/setup.py	Thu Nov 10 22:15:58 2016 -0800
+++ b/setup.py	Thu Nov 10 22:26:35 2016 -0800
@@ -589,6 +589,10 @@
               ['hgext/fsmonitor/pywatchman/bser.c']),
     ]
 
+sys.path.insert(0, 'contrib/python-zstandard')
+import setup_zstd
+extmodules.append(setup_zstd.get_c_extension('mercurial.zstd'))
+
 try:
     from distutils import cygwinccompiler