RFR: 694: Checking invalid email gives an exception

[Erik Helin]

Hi all,

please review this patch that ensures that contributors who do not have an OpenJDK username specify a valid name and
e-mail for a pull request's `HEAD` commit.

Testing:
- Added a new unit test
- `make test` passes on Linux x64

Thanks,
Erik

-------------

Commit messages:
 - 694

Changes: https://git.openjdk.java.net/skara/pull/837/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=837&range=00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-694
  Stats: 48 lines in 3 files changed: 45 ins; 1 del; 2 mod
  Patch: https://git.openjdk.java.net/skara/pull/837.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/837/head:pull/837

PR: https://git.openjdk.java.net/skara/pull/837