RFR: 45: Fix remaining integration test issues

[Robin Westberg via github.com]

Hi all,

Please review this fix that improves the error message when an incorrect repository is encountered in a merge PR, as well as adjusting the tests.

Best regards,
Robin

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Commits:
 - 67616fa4:	Improve merge error handling, make the test host consistent with real ones

Pull request:
http://git.openjdk.java.net/skara/pull/31

Webrev:
https://openjdk.github.io/cr/skara/31/webrev.00

Patch:
http://git.openjdk.java.net/skara/pull/31.diff

Fetch command:
git fetch https://github.com/openjdk/skara.git pull/31/head:pull/31