* 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

* test=develop

* update identity

* add unittest

* notest,test=mac_py3

* modify comment & testname

* test=document_fix

* update comment

* test=document_fix

* activate all of the CI