Extending the phpunit-version-unsupported error message

The original message did not provide any further pointers as to
what someone should do or look for, other than change their
version of phpunit (up? down?). This commit fixes that.
Merge branch 'hotfix/3743' into develop

Close #3743
Forward #3775
Forward #3762
Forward #3761
Merge pull request #3736 from Freeaqingme/phpunitSupportVersion

Extending the phpunit-version-unsupported error message
Forward #3766