In terminal Emacs, I found not highlight state of flymake even there is a
warning.
It can be visible if you set underline to the flymake's face.

How to reproduce:
1. cd emacs repo to ./lisp/progmode/
2. open js.el: $ emacs -Q -nw
4. M-x flymake-mode
3. goto-line 240 or 568 at js.el
   (there is warning around here, basically putting a space before end of
the line
    cause similar warning in docstring)
5. you can check it by flymake-goto-next-error, but it isn't visible.

Not sure this is related, flycheck highlight previous word with the same
error.

(checked on Emacs-26 branch and pulled 75bb482. This time I used bootstrap
option)

Thanks,
Yuta Yamada