This allows to make use of it when determining the rootdir etc.

…features

Merge master into features

Optimize/revisit determine_setup

approx() was updated in 9f3122f to work better with numpy arrays,
however at the same time the requirements were tightened from
requiring an Iterable to requiring a Sequence - the former being
tested only on interface, while the latter requires subclassing or
registration with the abc.

Since the ApproxSequence only used __iter__ and __len__ this commit
reduces the requirement to only what's used, and allows unregistered
Sequence-like containers to be used.

Since numpy arrays qualify for the new criteria, reorder the checks so
that generic sequences are checked for after numpy arrays.

This handles `header` similar to Python 3.7 does it, and forwards any
other keyword arguments to the Pdb constructor.

This allows for `__import__("pdb").set_trace(skip=["foo.*"])`.

Fixes pytest-dev#4416.

Merge master into features

…st-namespace

remove pytest namespace hook

This was documented before, but never enforced.  Passing non-strings could
have strange side-effects and enforcing a string simplifies other
implementation.

Ensure that node ids are printable

…reason

Custom reason support for "importorskip"