Fix bad change to cythonize.py script, re subprocess call

bin/cythonize.py

@@ -56,7 +56,7 @@ def process_pyx(fromfile, tofile):
     try:
         try:
             r = subprocess.call(['cython'] + flags + ['-o', tofile, fromfile],
-                                shell=True, env=os.environ) # See Issue #791
+                                env=os.environ) # See Issue #791
             if r != 0:
                 raise Exception('Cython failed')
         except OSError:

setup.py

@@ -144,7 +144,7 @@ def generate_cython(root, source):
     print('Cythonizing sources')
     p = subprocess.call([sys.executable,
                          os.path.join(root, 'bin', 'cythonize.py'),
-                         source], shell=True, env=os.environ)
+                         source], env=os.environ)
     if p != 0:
         raise RuntimeError('Running cythonize failed')