qiskit/util.py
def _filter_deprecation_warnings():
    """Apply filters to deprecation warnings.

    Force the `DeprecationWarning` warnings to be displayed for the qiskit
    module, overriding the system configuration as they are ignored by default
    [1] for end-users. Additionally, silence the `ChangedInMarshmallow3Warning`
    messages.

    TODO: on Python 3.7, this might not be needed due to PEP-0565 [2].

    [1] https://docs.python.org/3/library/warnings.html#default-warning-filters
    [2] https://www.python.org/dev/peps/pep-0565/
    """
    deprecation_filter = ('always', None, DeprecationWarning,
                          re.compile(r'^qiskit\.*', re.UNICODE), 0)

    # Instead of using warnings.simple_filter() directly, the internal
    # _add_filter() function is used for being able to match against the
    # module.
    try:
        warnings._add_filter(*deprecation_filter, append=False)
    except AttributeError:
        # ._add_filter is internal and not available in some Python versions.
        pass

    # Add a filter for ignoring ChangedInMarshmallow3Warning, as we depend on
    # marhsmallow 2 explicitly. 2.17.0 introduced new deprecation warnings that
    # are useful for eventually migrating, but too verbose for our purposes.
    warnings.simplefilter('ignore', category=ChangedInMarshmallow3Warning)
def _filter_deprecation_warnings():
    """Apply filters to deprecation warnings.

    Force the `DeprecationWarning` warnings to be displayed for the qiskit
    module, overriding the system configuration as they are ignored by default
    [1] for end-users. Additionally, silence the `ChangedInMarshmallow3Warning`
    messages.

    TODO: on Python 3.7, this might not be needed due to PEP-0565 [2].

    [1] https://docs.python.org/3/library/warnings.html#default-warning-filters
    [2] https://www.python.org/dev/peps/pep-0565/
    """
    deprecation_filter = ('always', None, DeprecationWarning,
                          re.compile(r'^qiskit\.*', re.UNICODE), 0)

    # Instead of using warnings.simple_filter() directly, the internal
    # _add_filter() function is used for being able to match against the
    # module.
    try:
        warnings._add_filter(*deprecation_filter, append=False)
    except AttributeError:
        # ._add_filter is internal and not available in some Python versions.
        pass

    # Add a filter for ignoring ChangedInMarshmallow3Warning, as we depend on
    # marhsmallow 2 explicitly. 2.17.0 introduced new deprecation warnings that
    # are useful for eventually migrating, but too verbose for our purposes.
    warnings.simplefilter('ignore', category=ChangedInMarshmallow3Warning)
Apply filters to deprecation warnings.

    Force the `DeprecationWarning` warnings to be displayed for the qiskit
    module, overriding the system configuration as they are ignored by default
    [1] for end-users. Additionally, silence the `ChangedInMarshmallow3Warning`
    messages.

    TODO: on Python 3.7, this might not be needed due to PEP-0565 [2].

    [1] https://docs.python.org/3/library/warnings.html#default-warning-filters
    [2] https://www.python.org/dev/peps/pep-0565/