diff -ur M2Crypto/tests/test_authcookie.py M2Crypto-0.21.1/tests/test_authcookie.py

--- M2Crypto/tests/test_authcookie.py	2011-01-15 20:10:05.000000000 +0100

+++ M2Crypto-0.21.1/tests/test_authcookie.py	2015-07-07 14:42:20.713482088 +0200

@@ -114,7 +114,7 @@

     def test_cookie_str_changed_exp(self):

         c = self.jar.makeCookie(self.exp, self.data)

         cout = c.output()

-        str = cout[:26] + '2' + cout[27:]

+        str = cout[:26] + chr(ord(cout[26])^1) + cout[27:]

         s = Cookie.SmartCookie()

         s.load(str)

         self.failIf(self.jar.isGoodCookieString(s.output()))

@@ -122,7 +122,7 @@

     def test_cookie_str_changed_data(self):

         c = self.jar.makeCookie(self.exp, self.data)

         cout = c.output()

-        str = cout[:36] + 'X' + cout[37:]

+        str = cout[:36] + chr(ord(cout[36])^1) + cout[37:]

         s = Cookie.SmartCookie()

         s.load(str)

         self.failIf(self.jar.isGoodCookieString(s.output()))

@@ -130,7 +130,7 @@

     def test_cookie_str_changed_mac(self):

         c = self.jar.makeCookie(self.exp, self.data)

         cout = c.output()

-        str = cout[:76] + 'X' + cout[77:]

+        str = cout[:76] + chr(ord(cout[76])^1) + cout[77:]

         s = Cookie.SmartCookie()

         s.load(str)

         self.failIf(self.jar.isGoodCookieString(s.output()))