When fixture setup crashes, immediately cancel all other fixture setups

[njsmith]

Fixes gh-120

[codecov]

Codecov Report

Merging #121 (b338795) into master (59da535) will increase coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #121      +/-   ##
==========================================
+ Coverage   91.28%   91.34%   +0.06%     
==========================================
  Files          16       16              
  Lines         574      578       +4     
==========================================
+ Hits          524      528       +4     
  Misses         50       50              

Impacted Files	Coverage Δ
pytest_trio/_tests/test_fixture_ordering.py	100.00% <100.00%> (ø)
pytest_trio/plugin.py	79.25% <100.00%> (ø)

[gc-ss]

LGTM. Couldn't get it to hang any longer.

This PR has two issues - one with formatting and one with the docs build. Anything I can help with to make the merge happen?

(formatting fix from me would be passing it through black :P)

Thank you Nathaniel for this!

[njsmith]

Yeah, we ought to switch to black, but haven't gotten around to it yet. (If you'd like to prepare a PR for that, feel free!)

I'm not sure what's going on the with docs build... the error message didn't make sense to me, and when I tried to reproduce it locally everything worked fine...

[njsmith]

Oh wait I see, there's a bug in towncrier! When I used towncrier 19.2.0, it worked correctly. When I upgrade to towncrier 21.3.0, it generates the history file header like:

pytest-trio 0.7.0 (not released yet)pytest-trio 0.7.0 (not released yet)
------------------------------------

I.e., it drops the +dev and it puts the headline string twice. Very odd.

[njsmith]

Looks like we're hitting twisted/towncrier#346

I guess we'll downgrade towncrier for the moment...