ui: ‘display-hint’ checks column number for the right port.

This fixes (rather: works around) something like:

  $ guix import pypi nipype -r >/dev/null
  […]
  hint: Backtrace:
  […]
     344:42  3 (display-hint "This indicates that the\npackage is a…" . #)
  In ice-9/boot-9.scm:
    1747:15  2 (with-exception-handler #<procedure 7f9ee8e5f120 at ic…> …)
  In guix/build/syscalls.scm:
    2334:35  1 (_)
     2323:8  0 (terminal-window-size _)

  guix/build/syscalls.scm:2323:8: In procedure terminal-window-size:
  In procedure terminal-window-size: Inappropriate ioctl for device

* guix/ui.scm (display-hint): Pass PORT to ‘terminal-columns’.

Change-Id: Ica0096aee5e6b2c19814ae5d71de9ffe9ab32430

guix/ui.scm

@@ -341,7 +341,7 @@ other objects that must match the 'format' escapes in MESSAGE."
   (display (colorize (G_ "hint: ")) port)
   (display
    ;; XXX: We should arrange so that the initial indent is wider.
-   (parameterize ((%text-width (max 15 (- (terminal-columns) 5))))
+   (parameterize ((%text-width (max 15 (- (terminal-columns port) 5))))
      (texi->plain-text (match arguments
                          (() (format #f message))
                          (_  (apply format #f message