* fix empty bugs for xpu

* fix empty bugs for xpu

* move python/paddle/fluid/tests/unittests/xpu to test/xpu

* update CMakeLists.txt

* remove xpu in fluid/tests/unittests/

* add path to op_test_xpu

* fix incorrect path

* update test script

* fix test_adadelta_op_xpu error

* update config

* re-blacken python code

* temporarily disable date and diff_py_file

* skip a format

* [CodeStyle] remove all future import

* revert test_error.py

* restore future import in example code

* use yapf to format all python file

* yapf exclude two unittests file for they rely on writing and reading file, and format will break them

* disable diff_py_file because too many diff files cause command following failed

* aaaa

* add some ops support fp16 in kunlun2

* fix gather op and add logsumexp op on kunlun

* update xpu depence

* update tests and fix elementwise_add

* add gather_op xpu, test=develop, test=kunlun

* fix ut, test=develop, test=kunlun

* fix the ut,test=develop, test=kunlun