Small improvement on FlushError can't update error message

Output in the error message the table name and the column name.

The same error message improvement that in the previous PR. I noticed that whatever path the code takes inside the loop, `pk_params[col._label]` is always assign so it's safe to move the `if` statement inside the loop checking for this key's value in the dictionary.
It's true but I think pk_params will never be that big that the extra lookup affects the performance (although maybe I'm wrong). This way legibility and simplicity may be affected.