fix pylint issues

From: @ngtony
Reviewed-by: @ouwenchang,@ouwenchang,@wangyue01
Signed-off-by: @wangyue01

enhance query image error message

bugfix and add pillow to requirements.txt

modify summary format

bugfix

use sample_id in summary

fix CI problem

url encode '/' as well

fix ut

fix ut

fix ut

fix uncertainty enable checking

fix review comment

enhance exception raising

enhance comment

fix UT

del unused arguments

fix UT

explainer_api UT change to pytest style

fix UT url

explainer encapsulator UT change to pytest style

remove unnecessary deepcopy

remove import copy

fix some coding style issues

json return null if ExplainManager returns None

use fromtimestamp

use fromtimestamp

wrong name

wrong json key

use offset as page offset

enhance comments

rm mock_explainer_api.py

update copyright year 2020

remove unused import