pytest --collect-only fails when 'fail under' is set on a configuration

[maurofaccenda]

Summary

My pyproject.toml have the following sections (among other):

[tool.pytest.ini_options]
minversion = '6.0'
addopts = '--quiet --cov'

[tool.coverage.run]
source = ['my_module']

[tool.coverage.report]
fail_under = 75

And some tools (such as VSCode Python's plugin) depends on pytest --collect-only. However, when running that it fails as it doesn't actually run the tests and it displays a coverage way below the real value.

Expected vs actual result

Expected:
when running pytest --collect-only I'd expect it only to fail if for some reason it collect the list of tests, ignoring the fail under parameter.

Actual result:
pytest --collect-only fails stating the coverage didn't reach the goal.

Reproducer

git clone https://github.com/maurofaccenda/pytest-cov-issue.git
cd pytest-cov-issue/
python3 -m venv venv
source ./venv/bin/activate
pip install pip --upgrade
pip install -r requirements.txt
pytest  # succeeds
pytest --collect-only  # fails
echo $?  # prints 1

Versions

pip list output:

Package        Version
-------------- -------
attrs          20.1.0
coverage       5.2.1
iniconfig      1.0.1
more-itertools 8.4.0
packaging      20.4
pip            20.2.2
pkg-resources  0.0.0
pluggy         0.13.1
py             1.9.0
pyparsing      2.4.7
pytest         6.0.1
pytest-cov     2.10.1
setuptools     44.0.0
six            1.15.0
toml           0.10.1

$ python --version
Python 3.8.2

$ pytest --version
pytest 6.0.1

Config

[tool.pytest.ini_options]
minversion = '6.0'
addopts = '--quiet --cov'

[tool.coverage.run]
source = ['my_module']

[tool.coverage.report]
fail_under = 75

Code

https://github.com/maurofaccenda/pytest-cov-issue

[maurofaccenda]

Maybe this is related to pytest alone, but as it wouldn't happen without pytest-cov, I thought it would make sense to create the issue here.