ci: Travis: Python 3.5.1 via Trusty
ci: Travis: Python 3.5.1 via Trusty

Python 3.5.0 caused flaky failures before
(https://github.com/pytest-dev/pytest/issues/5795).

This is pulled out of https://github.com/pytest-dev/pytest/pull/6435,
which adds code specific for Python < 3.5.2.

It only runs a specific test, while collecting everything to get
coverage of the version specific code around typing.

The-Compiler/pytest,Akasurde/pytest,The-Compiler/pytest,pytest-dev/pytest,markshao/pytest,nicoddemus/pytest,nicoddemus/pytest,RonnyPfannschmidt/pytest,alfredodeza/pytest