RFR: Python 3 compatibility for mercurial extension

[Robin Westberg]

Hi all,

Please review this change that makes the mercurial extension python 3 compatible.

Best regards,
Robin

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Commit messages:
 - Python 3 compatibility

Changes: https://git.openjdk.java.net/skara/pull/593/files
 Webrev: https://webrevs.openjdk.java.net/skara/593/webrev.00
  Stats: 28 lines in 1 file changed: 0 ins; 0 del; 28 mod
  Patch: https://git.openjdk.java.net/skara/pull/593.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/593/head:pull/593

PR: https://git.openjdk.java.net/skara/pull/593