* add unittest count of windows

* Reduce the number of retries

* Support python3.8

test=notest

* Fix install pr requirements.txt

* test=document_fix

* Add details to the summary and test it, test=document_fix

* Add set +e before example, test=document_fix

* Remove test code, test=document_fix

* Optimize summary information and test it, test=document_fix

* Remove test code, test=document_fix

* add timeout unittests retry

* modifed parameter use

* Restore file changes caused by pre-commit and test it, test=document_fix

* Change argument of checkout, test=document_fix

* Remove test code, test=document_fix

* add retry on mac

* fix some error

* fix with some errors

* add failed unittests retry on win system

* modified the value of retry times

* Modify data download function, and support unittests of inference APIs on windows, test=develop

* The import error compatible with py2 and py3, and fix unittests problems of inference APIs on Windows, test=develop

show unittest time even if unittest failed

* Show more possible problems with build_and_check in file paddle_build.sh, test=develop

* Remove test codes modified in file device.py for build_and_check, test=document_fix

* Fix missing blank space in file device.py, test=document_fix

* Final process via summary_check_problems function, test=document_fix

* turn on WITH_INFERENCE_API_TEST

* Count the time and packet size on windows

* fix conflit

* fix conflit

* fix conflit

* fix date-time funciton

* Add the option to execute unit tests only at night

* set ut nightly label for 3 cases.