[Integrated] RFR: 322: Improve error message on non-author /integrate

[Robin Westberg]

Changeset: 2b645bb3
Author:    Robin Westberg <rwestberg at openjdk.org>
Date:      2020-03-23 07:46:18 +0000
URL:       https://git.openjdk.java.net/skara/commit/2b645bb3

322: Improve error message on non-author /integrate

Reviewed-by: ehelin

! bots/pr/src/main/java/org/openjdk/skara/bots/pr/IntegrateCommand.java
! bots/pr/src/test/java/org/openjdk/skara/bots/pr/IntegrateTests.java