From b4588f1798fc1a6e1230b5fe962986dc2e3e2f74 Mon Sep 17 00:00:00 2001
From: Benjamin Peterson <benjamin@python.org>
Date: Thu, 3 May 2012 13:49:30 -0400
Subject: [PATCH] escape the % operator in string formatting

---
 CHANGELOG                     | 1 +
 _pytest/assertion/rewrite.py  | 2 +-
 testing/test_assertrewrite.py | 4 ++++
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG b/CHANGELOG
index 82e218dba..8f1ae8bab 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,6 +1,7 @@
 Changese between 2.2.3 and ...
 -----------------------------------
 
+- fix error message for rewritten assertions involving the % operator
 - fix issue 126: correctly match all invalid xml characters for junitxml
   binary escape
 - fix issue with unittest: now @unittest.expectedFailure markers should
diff --git a/_pytest/assertion/rewrite.py b/_pytest/assertion/rewrite.py
index 97eeb6623..dc0317b85 100644
--- a/_pytest/assertion/rewrite.py
+++ b/_pytest/assertion/rewrite.py
@@ -297,7 +297,7 @@ binop_map = {
     ast.Mult : "*",
     ast.Div : "/",
     ast.FloorDiv : "//",
-    ast.Mod : "%",
+    ast.Mod : "%%", # escaped for string formatting
     ast.Eq : "==",
     ast.NotEq : "!=",
     ast.Lt : "<",
diff --git a/testing/test_assertrewrite.py b/testing/test_assertrewrite.py
index c07f10dae..648ab2100 100644
--- a/testing/test_assertrewrite.py
+++ b/testing/test_assertrewrite.py
@@ -195,6 +195,10 @@ class TestAssertionRewrite:
             y = -1
             assert x + y
         assert getmsg(f) == "assert (1 + -1)"
+        def f():
+            x = range(10)
+            assert not 5 % 4
+        assert getmsg(f) == "assert not (5 % 4)"
 
     def test_call(self):
         def g(a=42, *args, **kwargs):