I have a project like this:
├── CHANGES.txt
├── LICENSE
├── MANIFEST.in
...
├── docs
│   └── index.rst
├── negar
│   ├── Negar.py
│   ├── Virastar.py
│   ├──         
        Maybe try:
package_data={'negar/data': ['data/*.dat']},
                                                                        I used data_files
data_files = [('', ['negar/data/untouchable.dat'])],
                                                                        The first problem is that I didn't import my data file into the package with MANIFEST.in file. I imported it like this:
include negar/data/*.dat
After that my data file already imported with my package install. but because I had mistakes in open my data files, python couldn't find it. this question helped me to find the right way Python Access Data in Package Subdirectory and now I use something like this:
import os
this_dir, this_filename = os.path.split(__file__)
DATA_PATH = os.path.join(this_dir, "data", "data.txt")
print open(DATA_PATH).read()