Hi,
With latest version of pip, it now forces to build wheel for every package, which causes incompatibilities (due to use of data_files and copying into not standard path) . I've attempted to add --binary=:all: --no-binary mypackage to the pip command, but it did not help. Only solution I found is to break bdist_wheel command in the setup.py, but it adds error messages during installation which can be improperly interpreted by end users.
That may be your best workaround for now, but in you should try to fix your package so that it can build a wheel. Pip is moving towards making bdist_wheel the only supported option, because supporting 'setup.py install' adds a lot of complexity, which is a strain on our limited resources and makes it more difficult to add new features elsewhere in the packaging ecosystem.
-n