Bump version to 0.21.0

[pquentin]

No description provided.

[codecov]

Codecov Report

Merging #2332 (14f1cea) into master (bcaa10a) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2332      +/-   ##
==========================================
+ Coverage   99.56%   99.59%   +0.03%     
==========================================
  Files         115      115              
  Lines       14873    14873              
  Branches     2841     2841              
==========================================
+ Hits        14808    14813       +5     
+ Misses         42       40       -2     
+ Partials       23       20       -3     

Impacted Files	Coverage Δ
trio/_version.py	100.00% <100.00%> (ø)
trio/tests/test_path.py	98.72% <0.00%> (-0.64%)	⬇️
trio/tests/test_ssl.py	99.86% <0.00%> (+0.55%)	⬆️
trio/_highlevel_ssl_helpers.py	100.00% <0.00%> (+11.76%)	⬆️

[pquentin]

I first hit pytest-dev/pytest#10008, and now I'm seeing the following reproducible issue with PyPy 3.8 nightly:

=================================== FAILURES ===================================
________________________ test_module_with_deprecations _________________________

recwarn_always = WarningsRecorder(record=True)

    def test_module_with_deprecations(recwarn_always):
        assert module_with_deprecations.regular == "hi"
        assert len(recwarn_always) == 0
    
        filename, lineno = _here()
>       assert module_with_deprecations.dep1 == "value1"
E       AttributeError: module 'trio.tests.module_with_deprecations' has no attribute 'dep1'

Last good: python: 3.8.13 (cac1d879afd59ae416c8ad9839a605e03a5c1187, May 25 2022, 23:30:12)
First bad: python: 3.8.13 (d12062ce6a2083741f6788501ace2ebf94923b5e, May 30 2022, 04:58:37)

[pquentin]

I opened https://foss.heptapod.net/pypy/pypy/-/issues/3758 for the PyPy issue. Let's wait a bit to see how those two issues evolve before releaseing 0.21.0.