Re-using the built-in tmpdir fixture fixes pytest-dev/pytest#1083
Also with latest pytest there's no need to use --assert=plain on py35 anymore
Fixes#3699Fixespytest-dev/pytest#1083
Previously we attempt to do some crazy things with import hooks
in order to attempt to automatically alias normally installed
dependencies as our vendored dependencies. This turned out to be
fairly fragile, so instead we'll manually patch sys.modules to
trigger the aliasing.
As part of this, we also drop support for the
PIP_NO_VENDOR_FOR_DOWNSTREAM environment variable because it was
never fully supported and now that we have wheel caching, actually
using it could possibly trigger a bad wheel to be cached. The new
mechanism requires some light patching by downstream to opt into
the mechanism, so they can also easily remove all of the files
in pip/_vendor/ except for __init__.py.
The Travis OSX builders are incredibly inconsistent for how long
they take to run our test suite. It is currently ranging anywhere
from ~15 minutes to well beyond 50 minutes, at which point it
times out.