Question

How can I suppress non-built-in warnings using the python -W{action:message:category:module:line} option?

Environment

I am using an official Python-based Docker image python:3.7.9 with the following setup:

$ python -V
Python 3.7.9
$ pip list | grep -e redis -e cryptography
cryptography           44.0.0
redis                  4.5.1
types-redis            4.6.0.11

Background

When I run tests on an older Python project (Python==3.7.9), I get the following warning:

  /usr/local/lib/python3.7/site-packages/_pytest/config/__init__.py:1728: CryptographyDeprecationWarning: Python 3.7 is no longer supported by the Python core team and support for it is deprecated in cryptography. A future release of cryptography will remove support for Python 3.7.

This warning seems to originate from the cryptography package, which is imported indirectly via the redis package:

if sys.version_info[:2] == (3, 7):
    warnings.warn(
        "Python 3.7 is no longer supported by the Python core team "
        "and support for it is deprecated in cryptography. A future "
        "release of cryptography will remove support for Python 3.7.",
        utils.CryptographyDeprecationWarning,
        stacklevel=2,
    )

Source: https://github.com/pyca/cryptography/blob/main/src/cryptography/__init__.py

I know that upgrading Python is the best radical solution, but right now I want to suppress only this particular warning cryptography.utils.CryptographyDeprecationWarning to focus on testing other parts of the project. However, I don’t know how to specify warnings that are not built-in by category.

To summarize my question, is there a way to correctly specify and suppress this non-built-in warning with a command line option – not by matching messages – but by specifying a warning category?

What I tried

Specifying a warning category name does not work.

For example:

$ pytest -Wignore::CryptographyDeprecationWarning
ERROR: while parsing the following warning configuration:

  ignore::CryptographyDeprecationWarning

This error occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/_pytest/config/__init__.py", line 1690, in parse_warning_filter
    category: Type[Warning] = _resolve_warning_category(category_)
  File "/usr/local/lib/python3.7/site-packages/_pytest/config/__init__.py", line 1729, in _resolve_warning_category
    cat = getattr(m, klass)
AttributeError: module 'builtins' has no attribute 'CryptographyDeprecationWarning'

Note: The -W option passed to pytest has the same behavior as if you had given it directly to Python.

Using the full module path fails to suppress the warning:

$ pytest -Wignore::cryptography.utils.CryptographyDeprecationWarning
============================================== test session starts ===============================================
platform linux -- Python 3.7.9, pytest-7.2.1, pluggy-1.2.0
rootdir: /app, configfile: pytest.ini
plugins: mock-3.10.0
collected 192 items                                                                                              

... # test contents

================================================ warnings summary ================================================
../usr/local/lib/python3.7/site-packages/_pytest/config/__init__.py:1728
  /usr/local/lib/python3.7/site-packages/_pytest/config/__init__.py:1728: CryptographyDeprecationWarning: Python 3.7 is no longer supported by the Python core team and support for it is deprecated in cryptography. A future release of cryptography will remove support for Python 3.7.
    m = __import__(module, None, None, [klass])

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
========================================= 192 passed, 1 warning in 5.20s =========================================

On the other hand, filtering by the message text works as expected:

$ pytest -W ignore:'Python 3.7 is no longer supported by the Python core team and support for it is deprecated in cryptography. A future release of cryptography will remove support for Python 3.7.'
=========================================================================================== test session starts ===========================================================================================
platform linux -- Python 3.7.9, pytest-7.2.1, pluggy-1.2.0
rootdir: /app/proj, configfile: pytest.ini
plugins: mock-3.10.0, anyio-3.7.1
collected 6 items                                                                                                                                                                                         

... # test contents 

============================================================================================ 6 passed in 0.04s ============================================================================================

This issue is the same when configuring filterwarnings in pytest.ini:

[pytest]  
# filterwarnings = ignore::CryptographyDeprecationWarning # Error
# filterwarnings = ignore::cryptography.utils.CryptographyDeprecationWarning # Does not suppress
filterwarnings = ignore:Python 3.7 is no longer supported by the Python core team and support for it is deprecated in cryptography. A future release of cryptography will remove support for Python 3.7. # Works

Furthermore, the same is true if the option is given directly to Python.

$ python -Wignore::CryptographyDeprecationWarning -m pytest
# => Invalid -W option ignored: unknown warning category: 'CryptographyDeprecationWarning'
# ... Tests run with options ignored.
$ python -Wignore::cryptography.utils.CryptographyDeprecationWarning -m pytest # ignored this option
# => Invalid -W option ignored: invalid module name: 'cryptography.utils'
# ... Tests run with options ignored.

$ python -W'ignore:Python 3.7 is no longer supported by the Python core team and support for it is deprecated in cryptography. A future release of cryptography will remove support for Python 3.7.' -m pytest 
# ... tests run with correctly suppressed CyptographyDeprecationWarning

I found that CryptographyDeprecationWarning extends from UserWarning, so I tried as follows, but it still did not work.

$ pytest -Wignore::UserWarning:cryptography.utils
# or
$ python -Wignore::UserWarning:cryptography.utils -m pytest

Notice: I want to do a temporary check, so I want to achieve this with a command line option without changing the code as much as possible.