Use with statement rather than try: finaly: x.close().
Travis: use system site packages in virtualenv.
Use stderr.splitlines rather than Popen(universal_newlines=True)

The reason for this is that universal_newlines takes the Popen files out of
bytes mode on python3.
Merge branch 'travis' of git://github.com/garyvdm/dulwich
Merge branch 'with' of git://github.com/garyvdm/dulwich