middleware: allow git and hg users to use email address instead of the username This commit also replaces __get_user('default') with a call to a more widely used User.get_default_user() function, and removes no longer really used __get_user() methods from both SimpleHg and SimpleGit.

[tox]
minversion = 1.8
envlist = py{26,27}-{pytest,nose}

[testenv]
setenv =
    PYTHONHASHSEED = 0
deps =
    nose: nose
    pytest: pytest
commands =
    nose: nosetests {posargs}
    pytest: py.test {posargs}