Fix exit code for command line errors

[crazymerlyn]

Fixes #3913

[nicoddemus]

Thaks a lot @crazymerlyn!

I'm surprised we don't have any tests for this. Please add a test which calls pytest with the wrong arguments and checks the correct return code. I believe something like this in acceptance_test.py would suffice:

def test_usage_error_code(testdir):
    result = testdir.runpytest('-unknown-option-')
    assert result.ret == EXIT_USAGEERROR

[nicoddemus]

Oh and I forgot: please target the features branch. Although this is a bug fix, it is still changing the outcome of the pytest command, so we better be safe and release this in 3.8. 👍

[codecov]

Codecov Report

Merging #3925 into features will increase coverage by <.01%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##           features    #3925      +/-   ##
============================================
+ Coverage     96.24%   96.24%   +<.01%     
============================================
  Files           108      108              
  Lines         23409    23419      +10     
============================================
+ Hits          22529    22539      +10     
  Misses          880      880

Flag	Coverage Δ
#doctesting	31.84% <40%> (+0.06%)	⬆️
#nobyte	93.5% <100%> (-0.01%)	⬇️
#numpy	31.41% <40%> (+0.06%)	⬆️
#pexpect	53.54% <57.14%> (ø)	⬆️
#pluggymaster	95.08% <100%> (+0.02%)	⬆️
#py27	94.61% <100%> (ø)	⬆️
#py34	93.89% <100%> (+0.02%)	⬆️
#py35	93.9% <100%> (+0.02%)	⬆️
#py36	94.82% <100%> (ø)	⬆️
#py37	94.06% <100%> (+0.02%)	⬆️
#trial	34.08% <40%> (+0.06%)	⬆️
#xdist	94.64% <100%> (ø)	⬆️

Impacted Files	Coverage Δ
src/_pytest/config/argparsing.py	93.85% <100%> (+0.19%)	⬆️
testing/acceptance_test.py	98.9% <100%> (ø)	⬆️

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[crazymerlyn]

Changelog entry fixed, test added and the pull request now targets the features branch.

[nicoddemus]

Thanks @crazymerlyn! Closing/reopening the PR to restart CI.

[coveralls]

Coverage increased (+0.02%) to 94.064% when pulling b01704c on crazymerlyn:fix-exit-code into 01df368 on pytest-dev:features.

[RonnyPfannschmidt]

pytest does not use gettext at all so why add it

[nicoddemus]

Oh right, totally missed that. Weird though, shouldn't flake8 catch that?

[crazymerlyn]

@RonnyPfannschmidt The default implementation of error function used it and I didn't want to change anything other than the error code.

[nicoddemus]

Oh right, it is used:

self.exit(EXIT_USAGEERROR, _("%(prog)s: error: %(message)s\n") % args)

Even though we don't translate pytest messages, I don't mind leaving it in as gettext is already being imported by argparser anyway. But want me to remove it @RonnyPfannschmidt?

[RonnyPfannschmidt]

@crazymerlyn thanks for the additional context
@nicoddemus thanks for the investigation

im a bit thorn between keeping similarity to imported code and limiting code scope, lets keep it as is for now