c extension is not required by default, so now it's not needed to che…

…ck if c code exists

setup.py

@@ -213,7 +213,7 @@ def get_ext_module_1(optional):
 )
 
 if custom_arg is None:
-    if impl == "PyPy" or not c_src_path.exists():
+    if impl == "PyPy":
         custom_arg = "py"
     else:
         custom_arg = "py" if pure_py else "c"