diff -r ff72bd52d56a -r 9d2b2df2c2ba tests/test-revlog-raw.py
--- a/tests/test-revlog-raw.py	Fri Mar 06 10:52:44 2020 +0100
+++ b/tests/test-revlog-raw.py	Fri Mar 06 13:27:41 2020 -0500
@@ -229,7 +229,7 @@
 
     # Gray Code. See https://en.wikipedia.org/wiki/Gray_code
     gray = lambda x: x ^ (x >> 1)
-    reversegray = dict((gray(i), i) for i in range(m))
+    reversegray = {gray(i): i for i in range(m)}
 
     # Generate (n * 2) bit gray code, yield lower n bits as X, and look for
     # the next unused gray code where higher n bits equal to X.