Change basic test case to be consistent with existing assertion rewriting

The code
```
x = 0
assert x == 1
```
will give the failure message 0 == 1, so it shouldn't be different as
part of an unroll

testing/test_assertrewrite.py

@@ -656,11 +656,11 @@ class TestAssertionRewrite(object):
         else:
             assert lines == ["assert 0 == 1\n +  where 1 = \\n{ \\n~ \\n}.a"]
 
-    def test_all_unroll(self):
+    def test_unroll_expression(self):
         def f():
             assert all(x == 1 for x in range(10))
 
-        assert "0 != 1" in getmsg(f)
+        assert "0 == 1" in getmsg(f)
 
     def test_custom_repr_non_ascii(self):
         def f():