Comment 3 for bug 1745886

Reviewed: https://reviews.mahara.org/8519
Committed: https://git.mahara.org/mahara/mahara/commit/d89c2041f1478589fdf33a009402fefa3327b9b6
Submitter: Robert Lyon (<email address hidden>)
Branch: master

commit d89c2041f1478589fdf33a009402fefa3327b9b6
Author: Rebecca Blundell <email address hidden>
Date: Tue Feb 13 11:11:30 2018 +1300

Bug 1745886: Deprecated plugin shows better error message

-made error message that displays for a partial plugin easier to follow
-replaced hard-coded string message with string variable
-replaced hard-coded string with the variable in the other 2 places it
occurred

note: I also found an almost duplicated function that contained the
string.

behatnotneeded

Change-Id: Ifda3bb2155e2adeb775aef8c72b4a90b7d202f17