fixes #1599

The main fix is to catch IOError when reading the data. The majority of the code change is removing the dependency on setuptools and pkg_resources in favor of the built-in pkgutils.

I tried moving to importlib_resources for Python < 3.7, but for some reason that API doesn't support directories of resources unless the directory is also a package. I'm not sure why this restriction is there, give that ResourceReader.open_resource supports directories (although is_resource doesn't). Instead, we need two versions, using theloader.get_resource_reader() API on Python 3, and the package path and loader.get_data() method on Python 2.