Modified validation for expected exceptions and warnings in pytest APIs

[fumedev]

CHANGED

• Added new validation checks to the raises function in src/_pytest/python_api.py to handle cases where expected_exception is () or None. If the input is invalid, a UsageError is now raised with a detailed error message.

CHANGED

• Implemented new validation logic in the warns function in src/_pytest/recwarn.py to handle scenarios where expected_warning is () or None. If the input is invalid, a TypeError is now raised with a detailed error message.

CHANGED

• Updated the xfail function in src/_pytest/mark/structures.py to include checks for raises being () or None when provided. In case of invalid input, a UsageError is now raised with a detailed error message.

These enhancements ensure that pytest.raises(), pytest.warns(), and pytest.mark.xfail() functions provide clearer and more informative error messages when encountering () or None as arguments.