UserModel: remove code duplication of User.get_by_username() UserModel.get_by_username() and User.get_by_username() implement the same logic and thus one should use the other instead of duplicating.

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

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