Add nice error message when objects are not equal but their repr is.

Author: nedtwigg

python/selfie-lib/selfie_lib/SelfieImplementations.py

@@ -270,13 +270,18 @@ def _toBeDidntMatch(expected: Optional[T], actual: T, fmt: LiteralFormat[T]) ->
                 f"Can't call `toBe_TODO` in {Mode.readonly} mode!"
             )
         else:
-            raise _selfieSystem().fs.assert_failed(
-                message=_selfieSystem().mode.msg_snapshot_mismatch(
-                    expected=repr(expected), actual=repr(actual)
-                ),
-                expected=expected,
-                actual=actual,
-            )
+            expectedStr = repr(expected)
+            actualStr = repr(actual)
+            if expectedStr == actualStr:
+                raise f"Value of type {type(actual)} is not `==` to the expected value, but they both have the same `repr` value:\n${expectedStr}"
+            else:
+                raise _selfieSystem().fs.assert_failed(
+                    message=_selfieSystem().mode.msg_snapshot_mismatch(
+                        expected=expectedStr, actual=actualStr
+                    ),
+                    expected=expected,
+                    actual=actual,
+                )
 
 
 def _assertEqual(