change _generate_op_module_signature get_module_file open with encodi…

…ng="utf-8",it fix some encode error in Chinese windows system.

python/mxnet/base.py

@@ -672,7 +672,7 @@ def get_module_file(module_name):
         module_path = module_name.split('.')
         module_path[-1] = 'gen_' + module_path[-1]
         file_name = os.path.join(path, '..', *module_path) + '.py'
-        module_file = open(file_name, 'w')
+        module_file = open(file_name, 'w', encoding="utf-8")
         dependencies = {'symbol': ['from ._internal import SymbolBase',
                                    'from ..base import _Null'],
                         'ndarray': ['from ._internal import NDArrayBase',