src layoutでのsetup.cfg
One commonly used package configuration has all the module source code in a subdirectory (often called the src/ layout),
# This example contains just the necessary options for a src-layout, set up the rest of the file as described above.
code:src_layout_example.cfg
package_dir=
=src
packages=find:
where=src
where=srcだけでよくなる
tests以下をexcludeする必要がない(testsはsrcと同じ階層)
参考