025 026 Splits ``field_name`` on ``.``, and use it as path in the nested ``entry`` 027 dictionary. If a value does not exist, returns None. 028 029 >>> get_field_value({"foo": 1, "bar": {"baz": 2, "qux": [3, 4]}}, "foo") UNEXPECTED EXCEPTION: KeyError('_source') Traceback (most recent call last): File "/usr/lib/python3.7/doctest.py", line 1329, in __run compileflags, 1), test.globs) File "<doctest swh.lister.cpan.lister.get_field_value[0]>", line 1, in <module> File "/var/lib/jenkins/workspace/DLS/tests-on-diff@2/.tox/py3/lib/python3.7/site-packages/swh/lister/cpan/lister.py", line 39, in get_field_value field_value = entry["_source"] KeyError: '_source' /var/lib/jenkins/workspace/DLS/tests-on-diff@2/.tox/py3/lib/python3.7/site-packages/swh/lister/cpan/lister.py:29: UnexpectedException