Error thrown while installing requirements on Windows

[andreatulimiero]

Full stack trace:

Collecting carbonara-idb (from -r .\requirements.txt (line 1))
  Using cached carbonara_idb-0.4.0.post2-py2-none-any.whl
Collecting carbonara-archinfo (from -r .\requirements.txt (line 2))
  Using cached carbonara_archinfo-7.7.9.14.post1-py2-none-any.whl
Collecting carbonara-pyvex (from -r .\requirements.txt (line 3))
  Using cached carbonara_pyvex-7.7.9.14.post3-py2-none-win32.whl
Collecting requests (from -r .\requirements.txt (line 4))
  Using cached requests-2.18.4-py2.py3-none-any.whl
Collecting appdirs (from -r .\requirements.txt (line 5))
  Using cached appdirs-1.4.3-py2.py3-none-any.whl
Collecting datasketch (from -r .\requirements.txt (line 6))
  Using cached datasketch-1.2.5-py2.py3-none-any.whl
Collecting r2pipe (from -r .\requirements.txt (line 7))
  Using cached r2pipe-0.9.8.tar.gz
    Complete output from command python setup.py egg_info:
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "c:\users\$USER\appdata\local\temp\pip-build-f8_abq\r2pipe\setup.py", line 2, in <module>
        import r2pipe
      File "r2pipe\__init__.py", line 45, in <module>
        from .native import RCore
      File "r2pipe\native.py", line 9, in <module>
        lib = WinDLL(find_library('r_core'))
      File "C:\Python27\Lib\ctypes\__init__.py", line 365, in __init__
        self._handle = _dlopen(self._name, mode)
    TypeError: expected string or Unicode object, NoneType found

    ----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in c:\users\$USER\appdata\local\temp\pip-build-f8_abq\r2pipe\