EnvironmentVariableFixture uses old-style upcalling

[Jonathan Lange]

Not actually sure if this is a problem:

    def setUp(self):
        Fixture.setUp(self)

Should say:

    def setUp(self):
        super(EnvironmentVariableFixture, self).setUp()

[Robert Collins (lifeless)]

Either is fine, as we don't have any multiple inheritance today.

[Robert Collins (lifeless)]

Bah, I missed this for 0.3.7. Will put it in for 0.3.8.