Fail gracefully when line number is out-of-bounds and negative

[jakevdp]

This fixes an issue I ran into that is similar to #752.

I don't have a self-contained repro for this failure, but an example of the failure is in the nightly CI for the JAX project: https://github.com/google/jax/actions/runs/4607513902/jobs/8142126075. The last few lines of the traceback looks like this:

INTERNALERROR> E                 reprtraceback = self.repr_traceback(excinfo_)
INTERNALERROR> E                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
INTERNALERROR> E               File "/opt/hostedtoolcache/Python/3.11.2/x64/lib/python3.11/site-packages/_pytest/_code/code.py", line 871, in repr_traceback
INTERNALERROR> E                 reprentry = self.repr_traceback_entry(entry, einfo)
INTERNALERROR> E                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
INTERNALERROR> E               File "/opt/hostedtoolcache/Python/3.11.2/x64/lib/python3.11/site-packages/_pytest/_code/code.py", line 822, in repr_traceback_entry
INTERNALERROR> E                 s = self.get_source(source, line_index, excinfo, short=short)
INTERNALERROR> E                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
INTERNALERROR> E               File "/opt/hostedtoolcache/Python/3.11.2/x64/lib/python3.11/site-packages/_pytest/_code/code.py", line 751, in get_source
INTERNALERROR> E                 lines.append(space_prefix + source.lines[line_index].strip())
INTERNALERROR> E                                             ~~~~~~~~~~~~^^^^^^^^^^^^
INTERNALERROR> E             IndexError: list index out of range

Reading through the source, I see that positive out-of-bound indices are already handled gracefully:

pytest/src/_pytest/_code/code.py

Lines 746 to 748 in 31d0b51

	if source is None or line_index >= len(source.lines):
	source = Source("???")
	line_index = 0

Given this, I suspect the only possible way to hit the error I'm seeing is if the list index is out of range and negative.

[nicoddemus]

Seems similar/duplicate to #10840.

[jakevdp]

Yep, looks like a duplicate. Consider this a +1 for getting that PR in ASAP!

[jakevdp]

It looks like that PR is stalled on lack of tests – would it help to pull in the tests I wrote here?