Requirement py>=1.4.22 is too low

[jayvdb]

setup.py requires py>=1.4.22 , and pytest>=2.7.0, however pytest 2.7.0 setup.py requires py>=1.4.25.

This causes problems as pip resolutions is not very good.
If someone installs pytest-xdist & pytest 2.7.0 together in that order, pip will use py>=1.4.22 and ignore py>=1.4.25. You can see that at https://travis-ci.org/jayvdb/my-ci-test/jobs/187902155

All is well if pytest-xdist bumps the requirement up to py>=1.4.25, and someone wants to install pytest 2.7.0 : See https://travis-ci.org/jayvdb/my-ci-test/builds/187901866 , which fakes that situation by first intalling py==1.4.25

However it fails again if someone wants to use the latest pytest , as it requires py>=1.4.29`. See https://travis-ci.org/jayvdb/my-ci-test/jobs/187913569#L241

[jayvdb]

Note : pip does not have a dependency resolver : pypa/pip#988 ; it needs our help..

[RonnyPfannschmidt]

Up for doing a PR?

[jayvdb]

Sure, but do you want the incomplete solution of bumping up to py==1.4.25 , or py>=1.4.29.
The latter has been tested; see https://travis-ci.org/jayvdb/pytest-xdist/builds/188018807 .

[jayvdb]

This is now much worse, as the setup.py now requires pytest>=3.0.0, and the latest pytest requires py>=1.4.33.

The result is it is especially difficult to depend on pytest-xdist with a pre-existing pytest, such as using the default pytest provided by Travis.
See mementoweb/py-memento-client#13 for some major problems caused on Travis Python 2.7 and Python 3.4 environment.