I believe "deprecated" at the end is the sort of dangling modifier
deprecated by English style books I have read. I felt it to be
sufficiently awkward and potentially confusing, at least for a moment,
to be worth a few minutes to report and change.  Another suggestion for
improvement:

"dict.has_key(key), now deprecated, is equivalent to key in dict, the
recommended replacement."

With or without the (optional) final phrase, this is smoother and
impossible to misread.