Fix setup.py.

setup.py

 from setuptools import setup
 from distutils.extension import Extension
 from Cython.Build import cythonize
-import os
+import os, errno
 import versioneer
 
 os.environ["CC"] = "gcc-5"
 os.environ["CXX"] = "g++-5"
 
 ext = Extension(name='prrt', sources=["prrt/*.pyx"])
+try:
+    os.remove(os.path.join(os.path.dirname(os.path.realpath(__file__)), "prrt/prrt.c"))
+except OSError as e:
+    if e.errno != errno.ENOENT:
+        raise
+
 ext_modules = cythonize(ext, gdb_debug=True)
 
+
 setup(
     name='prrt',
     version=versioneer.get_version(),