Otherwise, since requirements.txt is loaded into install_requires, any installationwhich manages to miss installing ddt could cause setuptools to freak out.E.g.here is a traceback from running tests of datalad    ======================================================================    ERROR: datalad.metadata.tests.test_aggregation.test_update_strategy    ----------------------------------------------------------------------    Traceback (most recent call last):      File "/home/yoh/anaconda-2018.12-3.7/envs/test-gitpython/lib/python3.7/site-packages/datalad/metadata/metadata.py", line 511, in _get_metadata        extractor_cls = extractors[mtype_key].load()      File "/home/yoh/anaconda-2018.12-3.7/envs/test-gitpython/lib/python3.7/site-packages/pkg_resources/__init__.py", line 2442, in load        self.require(*args, **kwargs)      File "/home/yoh/anaconda-2018.12-3.7/envs/test-gitpython/lib/python3.7/site-packages/pkg_resources/__init__.py", line 2465, in require        items = working_set.resolve(reqs, env, installer, extras=self.extras)      File "/home/yoh/anaconda-2018.12-3.7/envs/test-gitpython/lib/python3.7/site-packages/pkg_resources/__init__.py", line 786, in resolve        raise DistributionNotFound(req, requirers)    pkg_resources.DistributionNotFound: The "ddt>=1.1.1" distribution was not found and is required by GitPythonin conda environment.  Original commit74a0507which added ddt there unfortunately does not state the reason so probably wasjust a slip